Chapter: During Prostrations one should show his armpits and separate his forearms from his body
'Abdullah bin Malik
Narrated 'Abdullah bin Malik: Ibn Buhaina, "When the Prophet (ﷺ) prayed, he used to separate his arms from his body so widely that the whiteness of his armpits was visible."
Reference
Sahih al-Bukhari 390
In-book reference
Book 8, Hadith 42
USC-MSA web (English)
Vol. 1, Book 8, Hadith 385
Arabic Text
أَخْبَرَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا بَكْرُ بْنُ مُضَرَ، عَنْ جَعْفَرٍ، عَنِ ابْنِ هُرْمُزَ، عَنْ عَبْدِ اللَّهِ بْنِ مَالِكٍ ابْنِ بُحَيْنَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَ إِذَا صَلَّى فَرَّجَ بَيْنَ يَدَيْهِ حَتَّى يَبْدُوَ بَيَاضُ إِبْطَيْهِ. وَقَالَ اللَّيْثُ حَدَّثَنِي جَعْفَرُ بْنُ رَبِيعَةَ نَحْوَهُ.