Sahih Bukhari
Sahih Bukhari Volume 001, Book 012, Hadith Number 707.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 12. Charecteristics Of Prayer
Narated By Sahl bin Sa'd : The people were ordered to place the right hand on the left forearm in the prayer. Abu Hazim said, "I knew that the order was from the Prophet."