Ibn Abbas reported the Prophet ﷺ as saying: I have been commanded - according to the version of Hammad: Your Prophet ﷺ was commanded - to prostrate on seven (bones), and not to fold back the hair or the clothing.  

عَنِ النَّبِيِّ ﷺ قَالَ أُمِرْتُ قَالَ حَمَّادٌ أُمِرَ نَبِيُّكُمْ ﷺ أَنْ يَسْجُدَ عَلَى سَبْعَةٍ وَلاَ يَكُفَّ شَعْرًا وَلاَ ثَوْبًا  

I have been commanded, and sometimes the narrator said: Your prophet ﷺ was commanded to prostrate on seven limbs.  

عَنِ النَّبِيِّ ﷺ قَالَ أُمِرْتُ وَرُبَّمَا قَالَ أُمِرَ نَبِيُّكُمْ ﷺ أَنْ يَسْجُدَ عَلَى سَبْعَةِ آرَابٍ  

when a servant (of Allah) prostrates himself, the seven limbs, i.e, his face, his palms, his knees and his feet prostrate along with him.  

أَنَّهُ سَمِعَ رَسُولَ اللَّهِ ﷺ يَقُولُ إِذَا سَجَدَ الْعَبْدُ سَجَدَ مَعَهُ سَبْعَةُ آرَابٍ وَجْهُهُ وَكَفَّاهُ وَرُكْبَتَاهُ وَقَدَمَاهُ  

The Prophet ﷺ said: Both hands prostrate as the face prostrates. When one of you puts his face (on the ground) he should put his hands too (on the ground). And when he raises it, he should raise them too.  

إِنَّ الْيَدَيْنِ تَسْجُدَانِ كَمَا يَسْجُدُ الْوَجْهُ فَإِذَا وَضَعَ أَحَدُكُمْ وَجْهَهُ فَلْيَضَعْ يَدَيْهِ وَإِذَا رَفَعَ فَلْيَرْفَعْهُمَا