Sunan At-Tirmidhi

Narrated Abu Hurairah:that the Messenger of Allah (ﷺ) said: ""There is no favor due upon us from anyone, except that we have repaid him, with the exception of Abu Bakr. Verily upon us, there is a favor due to him, which Allah will repay him on the Day of Judgement. No one's wealth has benefited me as Abu Bakr's wealth has benefited me. And if I were to take a Khalil, then I would have taken Abu Bakr as a Khalil, and indeed your companion is Allah's Khalil