مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2054
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas said: When the Prophet (ﷺ) fell sick, he instructed Abu Bakr to lead the people in prayer. Then he felt a little better so he came out, and when Abu Bakr realised he was there, he wanted to step back. But the Prophet (ﷺ) gestured to him and sat down to the left of Abu Bakr, and he started to recite from where Abu Bakr had left off.
Musnad Ahmad 2055Its isnad is saheeh]