Sunan an-Nasa'i, Volume 2, Book 12, Hadith 1100 (DarusSalam) ⓘ

It was narrated from 'Abbas bin 'Abdul-Muttalib that: He heard the Messenger of Allah say: "When a person prostrates, seven parts of his body prostrate with him: his forehead, his two hands, his two knees and his two feet."

أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ عَبْدِ الْحَكَمِ، عَنْ شُعَيْبٍ، عَنِ اللَّيْثِ، قَالَ أَنْبَأَنَا ابْنُ الْهَادِ، عَنْ مُحَمَّدِ بْنِ إِبْرَاهِيمَ بْنِ الْحَارِثِ، عَنْ عَامِرِ بْنِ سَعْدِ بْنِ أَبِي وَقَّاصٍ، عَنْ عَبَّاسِ بْنِ عَبْدِ الْمُطَّلِبِ، أَنَّهُ سَمِعَ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏ "‏ إِذَا سَجَدَ الْعَبْدُ سَجَدَ مَعَهُ سَبْعَةُ آرَابٍ وَجْهُهُ وَكَفَّاهُ وَرُكْبَتَاهُ وَقَدَمَاهُ ‏" ‏ ‏.‏