Musnad Ahmad 1034:47

Abu al-Nadr narrated to us, Sharik narrated to us, from Abd al-Malik ibn Umayr, from Rib'i ibn Hirash, from Hudhayfah ibn al-Yaman, who said: It was the habit of the Prophet, peace and blessings of Allah be upon him, that when he took to his bed at night, he would place his right hand under his right cheek, then say: "O Allah, in Your name I live, and in Your name I die." And when he awoke at night, he would say: "Praise be to Allah, who gave us life after He caused us to die, and to Him is the resurrection."