مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3884
Musnad of Abdullah bin Mas'ood
AbuI-Ahwas said: ‘Abdullah used to say, narrating from the Prophet (ﷺ): “If I were to take a close friend from among my ummah, I would have taken Abu Bakr as a close friend."
Musnad Ahmad 3909lts isnad is saheeh, Muslim (2383)]