'A Muslim will not sleep while in a state of ritual impurity (janaba), and he should not sleep without being in a state of purity. If he does not find water then he should perform dry ablution (tayammum) with soil, for the spirit of a believer ascends to Allah Almighty and He meets it and blesses it. If his time of death was to have come when in a state [of purity], He places his spirit within the folds of His Mercy, and if his end has not come He sends it back [i.e. his spirit] with His guardian angels and they return it to his body.?