مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2223
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn ‘Abbas (رضي الله عنه) that he said: The Messenger of Allah (ﷺ) said on the day of at-Ta'if. “Whoever comes out to us of slaves, he is free.” So some slaves came out, among whom was Abu Bakrah, and the Messenger of Allah (ﷺ) set them free.
Musnad Ahmad 2229Hasan because of corroborating evidence; this is a da'eef is