It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "I have been commanded to prostrate on seven limbs: the nose, the forehead, the two palms and the tips of the fingers; and not to gather up hair or clothing."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10815