Sayyiduna Abdullah bin Abbas (may Allah be pleased with them) narrates that the Noble Prophet (peace and blessings be upon him) commanded to prostrate on seven (parts): two hands, two knees, the edges of the toes of both feet, and the forehead, and also forbade gathering the hair and clothes.
Hadith Referenceالمنتقى ابن الجارود / كتاب الصلاة / 199