The Prophet ﷺ said: "I have been commanded to prostrate on seven bones: on the forehead"- and he pointed with his hand- "on the nose, the hands, the knees and the ends of the feet."  

عَنِ النَّبِيِّ ﷺ قَالَ أُمِرْتُ أَنْ أَسْجُدَ عَلَى سَبْعَةِ أَعْظُمٍ عَلَى الْجَبْهَةِ وَأَشَارَ بِيَدِهِ عَلَى الأَنْفِ وَالْيَدَيْنِ وَالرُّكْبَتَيْنِ وَأَطْرَافِ الْقَدَمَيْنِ