عَنْ مَيْمُونَةَ زَوْجِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَتْ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ إِذَا سَجَدَ جَافَى حَتَّى يُرَى مَنْ خَلْفَهُ بَيَاضَ إِبْطَيْهِ
The wife of the Messenger, Sayyida Maymunah (may Allah be pleased with her), says: When the Messenger of Allah (peace and blessings be upon him) performed prostration, he would spread (his arms) so much that whoever was behind him could see the whiteness of his armpits.