The Prophet ﷺ said, "I have been ordered to prostrate on seven (bones) and not to tuck up the hair or garment." (Using translation from Bukhārī 816)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ «أُمِرْتُ أَنْ أَسْجُدَ عَلَى سَبْعَةٍ وَلَا أَكُفَّ شَعْرًا وَلَا ثَوْبًا»