Musannaf Ibn Abi Shayba 3:6064

Abu Khalid narrated to us, from Ibn ‘Ajlan, from ‘Amir ibn ‘Abd Allah ibn al-Zubayr, from his father, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) sat to supplicate, he would place his right hand upon his right thigh and his left hand upon his left thigh. He would gesture with his index finger and place his thumb upon his middle finger, and he would lay his left palm upon his knee.