Sahih al-Bukhari Book 62, Hadith 9
The Prophet (ﷺ) said, "If I were to take a Khalil, I would have taken him (i.e. Abu Bakr) as a Khalil, but
the Islamic brotherhood is better."
The Prophet (ﷺ) said, "If I were to take a Khalil, I would have taken Abu Bakr, but he is my brother and my companion (in Islam).
The people of Kufa sent a letter to Ibn Az-Zubair, asking about (the inheritance of) (paternal) grandfather. He replied that the right of the inheritance of (paternal) grandfather is the same as that of father if the father is dead) and added, "Allah's Messenger (ﷺ) said, ' If I were to take a Khalil from this nation, I would have taken him (i.e. Abu Bakr).