Sayyiduna Amr bin Hurayth (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) used to place the right hand over the left hand in the prayer, and sometimes he would also touch his beard during the prayer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3430