Firstly: 

The scholars differed concerning the du‘aa’ that is known as khutbat al-haajah and whether it is prescribed to quote it in the beginning of written works, books or letters. There are two views: 

The first view is that it is not Sunnah to write khutbat al-haajah when beginning to write anything.

Ibn ‘Allaan (may Allah have mercy on him) said: 

Recitation of the du‘aa’ that is known as khutbat al-haajah is limited to the giving of speeches and sermons, as in the case of Jumu‘ah, Eid and so on. This is what was done at the time of the Prophet (blessings and peace of Allah be upon him), and it has nothing to do with the writing of books. It was not quoted by at-Tirmidhi at the beginning of his books al-Jaami‘ and ash-Shamaa’il, or by Abu Dawood, although they both narrated the hadith. Their action indicates that it is only to be used in the circumstances mentioned. 

End quote from al-Futoohaat ar-Rabbaaniyyah (6/63), Dar Ihya’ at-Turaath al-‘Abari 

Al-Mulla ‘Ali al-Qaari (may Allah have mercy on him) said: 

The fact that most writers omitted it and did not act in accordance with the apparent meaning of this hadith – “Every speech in which there is no tashahhud (testimony of faith) is like a leprous hand” – indicates that the apparent meaning is not what is meant, so it is to be understood in the light of one of its interpretations. The interpretation that is more likely to be correct, in my view, is that the word speech in this hadith is to be understood as referring to the types of speech that were known at the time of the Prophet (blessings and peace of Allah be upon him), namely those that were delivered on Fridays, on Eid and so on, because compilation of books came after that. 

End quote from Jam‘ al-Wasaa’il Sharh ash-Shamaa’il (1/5), Mustafa al-Baabi al-Halabi edn. 

They quoted the following as evidence: 

1.

The letters that were sent by the Prophet (blessings and peace of Allah be upon him) to kings and rulers did not begin with this du‘aa’. Similarly, in many of the letters which he instructed to be written to the Muslims in order to explain the rulings on zakaah, diyah (blood money) and so on, he did not issue instructions that these letters should begin with khutbat al-haajah, and there is no mention in them of praising Allah and reciting the testimony of faith; rather there is only the Basmalah (the phrase Bismillah ir-Rahmaan ir-Raheem (In the name of Allah, the Most Gracious, the Most Merciful)). 

Ibn Hajar (may Allah have mercy on him) said: 

The letters of the Prophet (blessings and peace of Allah be upon him) to the kings and others were collected, and it was not seen in any one of them that he began with praising Allah; rather he began with the Basmalah.

End quote from Fath al-Baari (7/220) 

2.

Not one of the scholars who compiled books of hadith, such as al-Bukhaari, Muslim, and Ahmad ibn Hanbal, or books of fiqh such as ash-Shafaa‘i, or books of tafseer, Qur’anic sciences or Arabic grammar – we have not found that any one of them began his book with khutbat al-haajah. Similarly, we have not come across anyone who mentioned khutbat al-haajah in the books of etiquette, or who stated that it is recommended when writing and corresponding. Rather they mention it under the topic of marriage only. If that is Sunnah, then how could it have been omitted by the scholars of Islam who are the guardians of Islamic knowledge?? 

Ibn Hajar (may Allah have mercy on him) said: 

The books of the leading scholars, such as the shaykhs of al-Bukhaari, and the shaykhs of his shaykhs, and the people of his era – such as Maalik in al-Muwatta’, ‘Abd ar-Razzaaq in al-Musannaf, Ahmad in al-Musnad, Abu Dawood in as-Sunan, and countless others – did not begin their books with any du‘aa’. They did not write anything more than the Basmalah, and they are the majority. Few of them began their books with this du‘aa’. … Or it may be that they thought that this was only for speeches, not for books, as mentioned above. Therefore, some of them began their books with words praising Allah and the testimony of faith, as Muslim did… But the usual practice of the leading scholars was to begin their books of knowledge with the Basmalah. The same is also true of most books of essays. 

End quote from Fath al-Baari (1/9) 

The second view is that it is Sunnah to quote khutbat al-haajah at the beginning of books and letters.

This is the view of Imam Abu Ja‘far at-Tahhaawi (d. 229 AH – may Allah have mercy on him), as is clearly seen in the introduction to his book Mushkil al-Athaar. It is also the apparent meaning of the view favoured by Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him).  He began many of his essays with one of the proven formats of khutbat al-haajah, of which there are so many that it is difficult to enumerate them all. You can find them in Majmoo‘ al-Fataawa and Jaami‘ ar-Rasaa’il, and also in his books Dar’ at-Ta‘aarud, Bayaan Talbees al-Jahamiyyah and al-Akhnaa’iyyah. Similarly, al-‘Allaamah Ibn Qayyim al-Jawziyyah (may Allah have mercy on him) began his books at-Turuq al-Hukamiyyah and as-Salaah wa Ahkaam Taarikiha with this du‘aa’. 

At-Tahhaawi (may Allah have mercy on him) said: 

I begin – my book – with that which the Prophet (blessings and peace of Allah be upon him) instructed us to begin with, namely khutbat al-haajah, which was narrated from him via isnaads that I will mention later on, in sha Allah. It is: 

“Inna al-hamda  Lillaahi nasta’eenahu wa nastaghfiruhu, wa na’oodhu bihi min shuroori anfusinaa wa sayi’aati a’maalinaa. Man yahdih Illaahu falaa mudilla lahu wa man yudlil falaa haadiya lahu. Wa ashhadu an laa ilaaha ill-Allah wahdahu laa shareeka lah, wa ashhadu anna Muhammadan ‘abduhu wa rasooluhu (Verily, all praise is to Allah, we seek His help and His forgiveness. We seek refuge with Him from the evil of our own souls and from our bad deeds. Whomsoever Allah guides will never be led astray, and whomsoever Allah leaves astray, no one can guide. I bear witness that there is no god but Allah alone, with no partner or associate, and I bear witness that Muhammad is His slave and Messenger)” – then he quoted the verses [that are usually quoted following these words].

End quote from Sharh Mushkil al-Athaar (1/6) 

Ibn Taymiyah (may Allah have mercy on him) said: 

Hence it – i.e., khutbat al-haajah – is mustahabb and is done when addressing people and teaching them knowledge, such as teaching Qur’an, Sunnah and fiqh, exhorting the people and debating with them. It is mustahabb to begin with this khutbat al-haajah as prescribed in the Prophet’s teachings. 

The practice of the shaykhs of our time, whom we met and from whom, along with others, we acquired knowledge, is to start lessons of tafseer or fiqh in the mosques and schools and elsewhere with another du‘aa’, such as saying “Al-hamdu Lillahi Rabb il-‘Aalameen, wa sall Allahu ‘ala Muhammadin khaatam an-mursaleen, wa ‘ala aalihi wa sahbihi ajma‘een, wa radiya Allahu ‘anna wa ‘ankum wa ‘an mashaayikhina wa ‘an jamee‘ al-muslimeen – or wa ‘an as-saadat il-haadireena wa jamee‘ al-muslimeen (Praise be to Allah, the Lord of the Worlds, and may Allah send blessings upon Muhammad, the final Messenger, and upon all his family and companions, and may Allah be pleased with us and with you and with our shaykhs and with all the Muslims – or with the leaders who are present and all the Muslims).” 

I have also seen some people proposing marriage without the du‘aa’ that is prescribed. Each people has their own way, which is different from that of others. The hadith of Ibn Mas ‘ood does not speak specifically about marriage; rather it is a du‘aa’ for every occasion on which people address one another, and proposal of marriage comes under the same heading. Paying attention to the Sunnahs that are prescribed in word and deed in all acts of worship and customs is the way to perfect the straight path. As for anything other than that, even if it is not prohibited, it is nevertheless imperfect and lacking, for the best guidance is the guidance of Muhammad (blessings and peace of Allah be upon him). 

End quote from Majmoo‘ al-Fataawa (18/287) 

Ibn ‘Allaan (may Allah have mercy on him) said: 

It was said: Rather thus du‘aa’ of khutbat al-haajah may be recited on all occasions. Perhaps Abu Dawood and at-Tirmidhi recited it verbally at the beginning of their books, and omitted it in writing, and that is sufficient.

End quote from al-Futoohaat ar-Rabbaaniyyah (6/36) 

Shaykh al-Albaani (may Allah have mercy on him) said: 

This du‘aa’ may be used at the beginning of all speeches, whether it is on the occasion of marriage, the Friday (Jumu ‘ah) khutbah, or otherwise. It is not only for marriage – as some may think – and in some of the narrations of the hadith of Ibn Mas‘ood that is clearly stated, as mentioned above.

End quote from Khutbat al-Haajah (p. 36) 

They quoted the following as evidence for that: 

1.

There are many hadiths which state that the Prophet (blessings and peace of Allah be upon him) opened many of his khutbahs, exhortations and speeches with khutbat al-haajah, and he did not recite it only in the case of marriage. The Prophet (blessings and peace of Allah be upon him) spoke these words before Dimaam ibn Tha‘labah, and in that situation there was no marriage or Jumu‘ah or Eid. 

It was narrated from Ibn ‘Abbaas (may Allah be pleased with him) that Dimaad came to Makkah. … he said: O Muhammad, I treat people with incantation in the case of jinn possession, and Allah heals at my hands whomsoever He will. Do you want that? The Messenger of Allah (blessings and peace of Allah be upon him) said: “Praise be to Allah, We praise Him and seek His help. Whomsoever Allah guides, none can lead astray, and whomsoever He sends astray, none can guide. I bear witness that there is no god except Allah alone with no partner or associate and I bear witness that Muhammad is His slave and Messenger.” Dimaad said: Say these words of yours to me again. The Messenger of Allah (blessings and peace of Allah be upon him) repeated them three times and (Dimaad) said: I have heard the words of the soothsayers and the words of the magicians and the words of the poets, but I have never heard anything like these words of yours. You have scaled the heights of eloquence. He said: Give me your hand so that I may swear allegiance to you as a Muslim. So he gave him his oath of allegiance

Narrated by Muslim (868). 

There is also the hadith of Ibn Mas‘ood (may Allah be pleased with him) who said: The Messenger of Allah (blessings and peace of Allah be upon him) taught us the tashahhud in prayer, and the tashahhud in the du‘aa’ of khutbat al-haajah (when addressing others).

Narrated by at-Tirmidhi (1105); he said: A hasan hadith. 

They said: This may be recited on all occasions, whether it is a lesson, exhortation, khutbah, book, compilation, essay, or anything else. 

As-Sindi (may Allah have mercy on him) said: 

What appears to be the case is that khutbat al-haajah may be recited on the occasion of marriage and otherwise. So the individual should say this du‘aa’ so as to seek help thereby to fulfil and complete (his venture). 

End quote from his Haashiyah ‘ala Sunan an-Nasaa’i (3/105) 

2.

The general meaning of some reports, such as the report narrated in Sunan Abi Dawood (2118) from ‘Abdullah ibn Mas‘ood, who said: The Messenger of Allah (blessings and peace of Allah be upon him) taught us khutbat al-haajah, to be recited at weddings and on other occasions. 

3.

Some of the scholars begin their books with this khutbah, as was mentioned above in the case of Imam at-Tahhaawi (d. 229 AH), Ibn Tamiyah (d. 728 AH) and Ibn al-Qayyim (d. 751 AH). 

Discussion of the evidence:

Having reflected on the evidence presented by both sides, we can state that the first view is more likely to be correct, because of the strength of its evidence. 

As for our response to the evidence presented for the second view: 

The first piece of evidence does not any text the deal with the point concerning which opinions differed, which is starting books and other writings with these words. All the reports that are narrated about khutbat al-haajah only speak of verbal khutbahs and speeches (not written material). The practice of the Prophet (blessings and peace of Allah be upon him) when writing letters and messages to kings, rulers and others shows that he did not include khutbat al-haajah in any of them, and the actions of the Prophet (blessings and peace of Allah be upon him) serve to explain that which is not specified and is ambiguous. 

With regard to the second piece of evidence, it cannot be accepted, because the additional phrase (“in the case of marriage and otherwise”) was narrated via Abu Ishaaq, from Abu ‘Ubaydah, from ‘Abdullah ibn Mas‘ood, but this is an interrupted isnaad. Abu ‘Ubaydah did not hear directly from his father, the great Sahaabi ‘Abdullah ibn Mas‘ood (may Allah be pleased with him). This is what was mentioned in a comment by an-Nasaa’i on the hadith, after he quoted it in as-Sunan (1404). He said: Abu ‘Ubaydah did not hear anything directly from his father. 

Shaykh al-Albaani (may Allah have mercy on him) said: 

This additional phrase (“in the case of marriage and otherwise”) was narrated by Abu Dawood via Sufyaan from Abu Ishaaq, and appears to be the words of Ibn Mas‘ood, but Shu‘bah disagreed and said that it is the words of Abu Ishaaq, as he said: I said to Abu Ishaaq: Does this have to do with the occasion of marriage or something else? He said: It has to with every occasion. Narrated by at-Tayaalisi.

End quote from Khutbat al-Haajah (p. 10). 

If we assume that the additional material is saheeh, what is meant by it is speeches and exhortations on occasions other than marriage, and not writing and composing books. 

With regard to the third piece of evidence, it is a matter concerning which there is a difference of opinion, and that which is controversial cannot be quoted as evidence. Moreover, it is not appropriate to quote as evidence the opinion of some scholars against others. Rather what counts is the Prophetic Sunnah as narrated in reports that are attributed via complete chains of narration to the Prophet (blessings and peace of Allah be upon him), concerning his words or deeds. 

The fact that we say that it is not Sunnah does not mean that it is not permissible. There is no reason not to begin a book with the words of khutbat al-haajah sometimes, but that does not mean that it is encouraged or recommended. 

This is in addition to the fact that with regard to all of those who started some of their books with khutbat al-haajah, in most cases they did not do that. At-Tahhaawi only began one book with these words; in the rest of his books he did not do that. The same may be said about Ibn Taymiyah and Ibn al-Qayyim (may Allah have mercy on them both). 

Shaykh al-Albaani (may Allah have mercy on him) responded to that by saying:

It is not obligatory, such that we must not omit it; rather the opposite may be more correct, which is that it may be omitted sometimes, so that no one will think that it is obligatory.

End quote from Khutbat al-Haajah (p. 42) 

Such a response would be correct if it was established on the basis of clear evidence that the Prophet (blessings and peace of Allah be upon him) that he instructed people to begin letters with these words or did that himself. But because there is no proof to that effect, therefore the fact that the scholars did not do that supports the view that it is not Sunnah. 

Shaykh Bakr Abu Zayd (may Allah have mercy on him) said: 

We do not see these authors and scholars of Islam doing that. That includes Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him); in his books and fatwas, he sometimes begins with it (khutbat al-haajah) and sometimes he begins with other words. 

Therefore, what we see and hear nowadays of some writers always beginning their essays and speeches with these words, is something that I do not know of in the practice of the Prophet (blessings and peace of Allah be upon him) or of his Companions (may Allah be pleased with them), or of those who came after them and followed them in truth. Whoever makes a claim is required to produce evidence.                                                                                             

From this you will recognise the proper understanding of the authors of as-Sunan (may Allah have mercy on them) when they included khutbat al-haajah in Kitaab an-Nikaah (the Book of Marriage), and the statement of the scholars that it is prescribed to recite it before doing the marriage contract.

End quote from Tasheeh ad-Du‘aa’ (p. 454-455). See also: Mu‘jam al-Manaahi al-Lafziyyah (p. 590) 

Conclusion: the general practice in books and written works is to begin with the basmalah (Bismillah ir-Rahmaan ir-Raheem) or with general words of praise. As for khutbat al-haajah which includes specific phrases and Qur’anic verses, it is not Sunnah in books and other written works. Rather many of the scholars said that it is only encouraged in the case of the marriage contract, because when you research the matter you will find that dozens of hadith scholars and fuqaha’, in the books of fiqh and hadith, mention khutbat al-haajah in the chapters on marriage and the etiquette and rulings thereon; if we were to quote examples thereof, it would take a great deal of time. 

And Allah knows best.