Answered by Shaykh Faraz Rabbani
Someone seems to claim that in the hanafi maddhab, wudu is invalidated by simply lying down. Is this true?
Answer:
Wudu is broken if one sleeps with one’s rear not firmly on the ground.
If dosing deeply, such that you can’t understand most of the speech around you, wudu is broken.
Light dosing, which is if you can understand most speech around you, does not break wudu. [allfrom Durr and Radd]
Wassalam,
Faraz Rabbani