مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3305
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas said: I was behind the Prophet (ﷺ) when he prostrated, and the whiteness of his armpits could be seen when he prostrated.
Musnad Ahmad 3328Saheeh because of corroborating evidence; this is a da'eef i