Ibn Abbas saw a man prostrating with his forearms spread flat on the ground. Ibn Abbas remarked, "That is how a dog crouches. I saw the Messenger of Allah ﷺ, when he prostrated, the whiteness of his armpits was visible."
حدثنا يزيد أخبرنا ابن أبي ذئب
رأى ابن عباس رجلا ساجدا قد ابتسط ذراعيه فقال ابن عباس هكذا يربض الكلب رأيت رسول الله ﷺ إذا سجد رأيت بياض إبطيه