Ibn Al-Qayyim (may Allaah have mercy on him) mentioned three opinions concerning the circumcision of the Prophet (peace and blessings of Allaah be upon him). He said: 

There are different opinions on this matter: 

1 – That he was born circumcised 

2 – That Jibreel circumcised him when he split open his chest 

3 – That his grandfather ‘Abd al-Muttaalib circumcised him according to the Arab custom of circumcising their sons. 

Tuhfat al-Mawlood, p. 201. 

With regard to the first opinion, Ibn al-Qayyim narrated many ahaadeeth in the book mentioned which indicate this, but he ruled all of them to be da’eef (weak). Then he mentioned that if a child is born circumcised, this is a defect and it is a not a sign of virtue as some people think. 

And he said: 

It was said that Caesar the king of Rome whom Imru’ul-Qays came to visit was born like that (i.e., uncircumcised) and Imru’ul-Qays entered upon him in the baths and saw him like that, and composed a line of verse mocking him for being uncircumcised: 

He scorned him because he was not circumcised, and he regarded his being born like that as a defect. This line of verse was one of the reasons that motivated Caesar to poison Imru’ul-Qays and he died. 

The Arabs used to think of the act of circumcision as being something virtuous, but not the feature itself.  

Ibn al-Qayyim said: Allaah sent our Prophet from amongst the Arabs, and He gave him attributes of physical perfection and made him of fine lineage. So how could it be possible that he was born circumcised? It was said that circumcision was one of the words with which Allaah tested His Close Friend Ibraaheem, and he fulfilled this world, and the most severely tested of mankind are the Prophets, then the next best and the next best. The Prophet listed circumcision as one of the features of the fitrah, and being tested with this and carrying out this command with patience will multiply the reward. It is more befitting that the Prophet (peace and blessings of Allaah be upon him) should not miss out on this virtue and that Allaah should honour him in the same way as He honoured Ibraaheem, because he is more virtuous than any other Prophet. 

Tuhfat al-Mawlood, 205-206 

With regard to the second opinion, he said: 

The hadeeth about the angel splitting open his heart was narrated through many isnaads going back to the Prophet; it does not mention in any of them that Jibreel circumcised him, except in this hadeeth which is (shaadhdh ghareeb (odd and strange). 

Tuhfat al-Mawlood, p. 206 

With regard to the third opinion, he said: 

Ibn al-‘Adeem said: It says in some reports that his grandfather ‘Abd al-Muttalib circumcised him on the seventh day. He said, this seems to be the correct view and closest to reality.  

Tuhfat al-Mawlood, p. 206 

Ibn al-Qayyim said in Zaad al-Ma’aad (1/82): 

This issue arose between two righteous men. One of them wrote a book saying that the Prophet (peace and blessings of Allaah be upon him) was born circumcised and compiled in it ahaadeeth which are not sound at all. His name was Kamaal al-Deen ibn Talhah. He was criticized by Kamaal al-Deen ibn al-‘Adeem who explained that the Prophet (peace and blessings of Allaah be upon him) was circumcised according to the custom of the Arabs. As this was the custom of all of the Arabs, there is no need for a report (to prove that he was circumcised). 

And Allaah knows best.