Ablution (Wudu) Bulugh al-Maram 38
Translation
Narrated Abu Huraira (rad)
Allah’s Messenger (ﷺ) said: “When one of you wakes up from his sleep, he must not put his hand in a utensil till he washed it three times, for he does not know where his hand was (while he slept)”.[Agreed upon. This is Muslim’s version].