Musannaf Ibn Abi Shayba 3:1570

Abu Mu'awiyah narrated to us, Hafs narrated to us, from Layth, from Mujahid, that he used to dislike placing the right [hand] upon the left. He would say: "Upon the palm or upon the wrist." And he would say: "Above that." And he would say: "The People of the Book do it."