Musannaf Ibn Abi Shayba 3:6062

Waki’ narrated to us, from ‘Asim ibn Qudamah, from Malik ibn Numayr al-Khuza’i, from his father, who said: I saw the Prophet, may Allah bless him and grant him peace, sitting in the prayer, placing his right hand upon his thigh, gesturing with his finger.