The Description Of The Prayer, With What It Begins And Ends. The Description Of Bowing And Moderation Therein, And Of Prostration And Moderation Therein. Tashah-hud After Each Two Rak'ah Of Four Rak'ah Prayers. Description Ol Sitting Between The Two Prostrations, And In The First Tashah-hud Sahih Muslim 495 a
Translation
'Abdullah b. Malik ibn Bujainah reported
When the Prophet (ﷺ) prostrated, lie spread out his arms so that the whiteness of his armpits was visible.