Musnad Ahmad 1080:0

Narrated to us by Abd al-Razzaq, who said: Narrated to us Ma'mar, from al-Zuhri, from Sa'id ibn al-Musayyib, from his father, al-Musayyib ibn Hazn, who said: When the death of Abu Talib approached, the Messenger of Allah (ﷺ) came to him and found Abu Jahl ibn Hisham and Abdullah ibn Abi Umayyah ibn al-Mughirah with him. The Messenger of Allah (ﷺ) said: "O my uncle, say: 'There is no god but Allah,' a word by which I will testify for you before Allah." Abu Jahl and Abdullah ibn Abi Umayyah said: "O Abu Talib, will you turn away from the religion of Abdul-Muttalib?" They continued to speak to him until the last thing he said to them was upon the religion of Abdul-Muttalib, and he refused to say: "There is no god but Allah." The Messenger of Allah (ﷺ) said: "I will surely seek forgiveness for you as long as I am not forbidden from doing so." Then Allah, the Exalted, revealed: "It is not for the Prophet and those who have believed to ask forgiveness for the polytheists, even if they were relatives, after it has become clear to them that they are companions of Hellfire." And He revealed concerning Abu Talib: "Indeed, you do not guide whom you like, but Allah guides whom He wills."