Mishkat al-Masabih

Hudhaifa said that when the Prophet lay down on his bed at night he placed his hand under his cheek, and would then say, "O God, in Thy name I die and live." When he awoke he said, "Praise be to God who has given us life after causing us to die,* and to whom we shall be resurrected." *Behind this phrase probably lies the idea expressed in Qur’an, xxxix, 42 which says, "It is God who takes the souls at the time of their death, and those which do not die during their sleep." Bukhari transmitted it, Muslim transmitting from al-Bara’.