Musnad Ahmad 1783

It was narrated that al-‘Abbas said: I entered upon the Messenger of Allah (ﷺ) when his wives were with him, so they covered themselves in front of me, except Maimoonah. He said: "There is no one in this house who witnesses the administration of medicine in the side of the mouth but he should be treated in the same way, but my instruction does not include al-"Abbas.” Then he said: "Tell Abu Bakr to lead the people in prayer.” "A"ishah said to Hafsah: Tell him that Abu Bakr is a man who, if he stands in your place, will weep, He said: “Tell Abu Bakr to lead the people in prayer." So he stood up and prayed, then the Prophet (ﷺ) felt a little better, so Abu Bakr retreated a little, wanting to move backwards, but [the Prophet (ﷺ)] sat beside him, then he started to recite.