The Prophet ﷺ was ordered (by Allah) to prostrate on seven parts and not to tuck up the clothes or hair (while praying). Those parts are: the forehead (along with the tip of nose), both hands, both knees, and (toes of) both feet.
عَنِ ابْنِ عَبَّاسٍ أُمِرَ النَّبِيُّ ﷺ أَنْ يَسْجُدَ عَلَى سَبْعَةِ أَعْضَاءٍ وَلاَ يَكُفَّ شَعَرًا وَلاَ ثَوْبًا الْجَبْهَةِ وَالْيَدَيْنِ وَالرُّكْبَتَيْنِ وَالرِّجْلَيْنِ
The Messenger of Allah ﷺ had been commanded to prostrate on seven (bones) and forbidden to fold back hair and clothing.
عَنِ ابْنِ عَبَّاسٍ أُمِرَ النَّبِيُّ ﷺ أَنْ يَسْجُدَ عَلَى سَبْعٍ وَنُهِيَ أَنْ يَكْفِتَ الشَّعْرَ وَالثِّيَابَ
"The Prophet ﷺ was commanded to prostrate on seven parts of his body and not to tuck up his hair or his garment."
أُمِرَ النَّبِيُّ ﷺ أَنْ يَسْجُدَ عَلَى سَبْعَةِ أَعْضَاءٍ وَلاَ يَكُفَّ شَعْرَهُ وَلاَ ثِيَابَهُ
The Messenger of Allah ﷺ said: "I have been commanded to prostrate on seven, and not to tuck up my hair nor my garment: the forehead, the nose, the hands, the knees and the feet."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ أُمِرْتُ أَنْ أَسْجُدَ عَلَى سَبْعَةٍ لاَ أَكُفَّ الشَّعْرَ وَلاَ الثِّيَابَ الْجَبْهَةِ وَالأَنْفِ وَالْيَدَيْنِ وَالرُّكْبَتَيْنِ وَالْقَدَمَيْنِ
[Machine] Narrated by Ibn Abbas: The Prophet ﷺ was ordered to prostrate on seven body parts, and he was forbidden to cover his hair or garment.
عَنِ ابْنِ عَبَّاسٍ أُمِرَ النَّبِيُّ ﷺ أَنْ يَسْجُدَ عَلَى سَبْعٍ وَنُهِيَ أَنْ يَكُفَّ شَعْرًا أَوْ ثَوْبًا