مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3855
Musnad of Abdullah bin Mas'ood
It was narrated that Ibn Mas'ond (رضي الله عنه) said: The Messenger of Allan (ﷺ) said: "If I were to take anyone as a close friend, I would have taken Ibn Abu Quhafah (i.e., Abu Bakr) as a close friend.”
Musnad Ahmad 3878Its isnad is saheeh, Muslim (2383)]