سُنَنُ النَّسَائِيِّ
Sunan an-Nasa’i 1108
The Book of The At-Tatbiq (Clasping One's Hands Together)
Description of prostration
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ أَنْبَأَنَا إِسْمَاعِيلُ، قَالَ حَدَّثَنَا دَاوُدُ بْنُ قَيْسٍ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ بْنِ أَقْرَمَ، عَنْ أَبِيهِ، قَالَ صَلَّيْتُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَكُنْتُ أَرَى عُفْرَةَ إِبْطَيْهِ إِذَا سَجَدَ .
It was narrated from 'Ubaidullah bin Abdullah bin Aqram that his father said: "I prayed with the Messenger of Allah (ﷺ) and I used to see the whiteness of his armpits when he prostrated."
Sunan an-Nasa'i, 1108Sahih (Darussalam)