It is narrated from Hazrat Abu Huraira that the Messenger of Allah said: When any of you gets up at night, he should not put his hand into the water until he has washed it three times, because he does not know where his hand spent the night.

Hazrat Abu Huraira narrates that the Messenger of Allah said: When any one of you wakes up from sleep, he should pour water on his hand three times before putting it into the vessel, because he does not know where his hand spent the night.

Hazrat Abu Huraira narrates that the Messenger of Allah said: When any one of you wakes up at night, he should not put his hand into the vessel before washing it.

Ibrahim says that when a person wakes up from sleep, he should not put his hand into the vessel before washing it.

Hazrat Sha'bi says that the one who is asleep and the one who is awake are equal; when ablution becomes obligatory upon him, he should not put his hands into the vessel before washing them.

Ibrahim says that when the hadith of Abu Hurairah was narrated before the students of Abdullah, they would say: "What will Abu Hurairah do with that 'mahr' which is in Madinah?" 'Mahr' refers to a rock in which a lot of water is absorbed. Pools of water are made from it. (Al-Nihayah 5/259)