Praise be to Allaah.

 The scholars differed concerning the ruling on saying Bismillaah in wudoo’. 

Imam Ahmad was of the view that it is obligatory, and he quoted as evidence the hadeeth narrated from the Prophet (peace and blessings of Allaah be upon him), according to which he said: “There is no wudoo’ for the one who does not mention the name of Allaah.” (Narrated by al-Tirmidhi, 25; classed as hasan by al-Albaani in Saheeh al-Tirmidhi. See al-Mughni, 1/145) 

The majority of scholars – including Imam Abu Haneefah, Imam Maalik and Imaam al-Shaafa’i – and according to one view narrated from Imam Ahmad, are of the view that saying Bismillaah is one of the Sunnahs of wudoo’, and that it is not obligatory. 

They quoted evidence for its not being obligatory, such as: 

1 – The Prophet (peace and blessings of Allaah be upon him) taught a man how to do wudoo’, and said to him: “Do wudoo’ as Allaah has commanded you.” (Narrated by al-Tirmidhi, 302; classed as saheeh by al-Albaani in Saheeh al-Tirmidhi, 247). This is referring to the words of Allaah (interpretation of the meaning): 

“O you who believe! When you intend to offer As-Salaah (the prayer), wash your faces and your hands (forearms) up to the elbows, rub (by passing wet hands over) your heads, and (wash) your feet up to the ankles”

[al-Maa'idah 5:6]

And there is no mention of saying Bismillaah in what Allaah commands here. See al-Majmoo’ by al-Nawawi, 1/346 

Abu Dawood (856) narrated a more complete version of this hadeeth, which more clearly demonstrates that it is not obligatory to say Bismillaah when doing wudoo’. 

It was narrated from Abu Hurayrah that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: The prayer of any one of you is not complete unless he does wudoo’ properly as enjoined by Allaah. So he should wash his face and his hands up to the elbows, and wipe his head, and wash his feet up to the ankles…” 

The Prophet (peace and blessings of Allaah be upon him) did not mention saying Bismillaah, which indicates that it is not obligatory.  See al-Sunan al-Kubra by al-Bayhaqi, 1/44 

2 – Many of those who described the wudoo’ of the Prophet (peace and blessings of Allaah be upon him) did not mention that he said Bismillaah; if it was obligatory it would have been mentioned. 

See al-Sharh al-Mumti’, 1/130 

This is the view favoured by many of the Hanbalis such as al-Khuraqi and Ibn Qudaamah. 

See al-Mughni, 1/145; al-Insaaf, 1/128 

Among contemporary scholars, this view is favoured by Shaykh Muhammad ibn Ibraaheem and Muhammad ibn ‘Uthaymeen (may Allaah have mercy on them both). 

See: Fataawa al-Shaykh Muhammad ibn Ibraaheem, 2/39; al-Sharh al-Mumti’, 1/130, 300) 

They responded in two ways to the hadeeth which is quoted by those who say that saying Bismillaah is obligatory: 

1 – That the hadeeth is da’eef (weak). 

It was classed as da’eef by a number of scholars including Imam Ahmad, al-Bayhaqi, al-Nawawi and al-Bazzaar. 

Imam Ahmad was asked about saying Bismillaah when doing wudoo’, and he said: There is no sound hadeeth concerning that, and I do not know of any hadeeth that has a jayyid (good) isnaad to support that. Al-Mughni, 1/145 

See al-Sunan al-Kubra by al-Bayhaqi, 1/43; al-Majmoo’, 1/343; Talkhees al-Habeer, 1/72 

2 – If the hadeeth is saheeh, then what it means is “no perfect wudoo’” and not “no valid wudoo’”. See al-Majmoo’, 1/347; al-Mughni, 1/146 

Based on this, then the hadeeth – if it is saheeh – indicates that it is mustahabb to say Bismillaah, but it is not obligatory. And Allaah knows best. 

Based on this, if a Muslim does wudoo’ and does not say Bismillaah, then his wudoo’ is valid, but he is missing out on the reward for doing this Sunnah. To be on the safe side, the Muslim should not omit to say Bismillaah when doing wudoo’.