Musnad Abu Ya'la al-Mawsili 167:3

Abu Khaythama narrated to us, Yahya ibn Sa'id 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 for the Tashahhud, he would say it like this—and Yahya placed his right hand upon his right thigh and his left [hand] upon his left thigh. He pointed with his index finger, and his gaze did not go beyond his pointing.