Musannaf Ibn Abi Shayba 3:1566

Yazid narrated to us, he said: Al-Hajjaj ibn Abi Zaynab informed us, he said: Abu Uthman narrated to me that the Prophet, may Allah bless him and grant him peace, passed by a man who was praying and had placed his left hand upon his right. The Prophet, may Allah bless him and grant him peace, took his right hand and placed it upon his left.