Jami` at-Tirmidhi Book 49, Hadith 58
that the Messenger of Allah (ﷺ) said: "Stick to the two after me, Abu Bakr and 'Umar."
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.
"We were sitting with the Prophet (ﷺ) and he said: 'I do not know how long I will be with you, so stick to the two after me,' and he signaled towards Abu Bakr and 'Umar."