Sahih al-Bukhari Book 62, Hadith 8
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).
We used to compare the people as to who was better during the lifetime of Allah's Messenger (ﷺ) . We used to regard Abu Bakr as the best, then `Umar, and then `Uthman .
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."