Sahih Bukhari Volume 2, Book 23, Hadith Number 442.
Narated By Said bin Al-Musaiyab : From his father: When the time of the death of Abu Talib approached, Allah’s Apostle went to him and found Abu Jahl bin Hisham and ‘Abdullah bin Abi Umaiya bin Al-Mughira by his side. Allah’s Apostle said to Abu Talib, “O uncle! Say: None has the right to be worshipped but Allah, a sentence with which I shall be a witness (i.e. argue) for you before Allah. Abu Jahl and ‘Abdullah bin Abi Umaiya said, “O Abu Talib! Are you going to denounce the religion of Abdul Muttalib?” Allah’s Apostle kept on inviting Abu Talib to say it (i.e. ‘None has the right to be worshipped but Allah’) while they (Abu Jahl and Abdullah) kept on repeating their statement till Abu Talib said as his last statement that he was on the religion of Abdul Muttalib and refused to say, ‘None has the right to be worshipped but Allah.’ (Then Allah’s Apostle said, “I will keep on asking Allah’s forgiveness for you unless I am forbidden (by Allah) to do so.” So Allah revealed (the verse) concerning him (i.e. It is not fitting for the Prophet and those who believe that they should invoke (Allah) for forgiveness for pagans even though they be of kin, after it has become clear to them that they are companions of the fire (9.113).