Sahih Muslim 491
Sahih Muslim · Book 4: The Book of Prayers · The Limbs Of Prostration And The Prohibition Of Tucking Up One's Hair And Garment Or Having Ones Hair In A Braid When Praying
It was narrated from Al-'Abbas bin 'Abdul Muttalib that he heard the Messenger of Allah (ﷺ) say:
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ ، حَدَّثَنَا بَكْرٌ، - وَهُوَ ابْنُ مُضَرَ - عَنِ ابْنِ الْهَادِ ، عَنْ مُحَمَّدِ بْنِ إِبْرَاهِيمَ ، عَنْ عَامِرِ بْنِ سَعْدٍ ، عَنِ الْعَبَّاسِ بْنِ عَبْدِ الْمُطَّلِبِ ، أَنَّهُ سَمِعَ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " إِذَا سَجَدَ الْعَبْدُ سَجَدَ مَعَهُ سَبْعَةُ أَطْرَافٍ وَجْهُهُ وَكَفَّاهُ وَرُكْبَتَاهُ وَقَدَمَاهُ " .
"When a person prostates, he prostates on seven part of the body: His face, his hands, his knees and his feet."