Answered by Shaykh Faraz Rabbani
Can you clarify your opinion on sleeping while sitting and whether it invalidates your wudu. Both with and without leaning against something. Because I have a book, Essential Hanafi Handbook of Fiqh, a translation of Qazi Thanaa Ullah’s Mala Budda Minhu. In it, it says that “sleeping; either on one’s back or side, or propped up against something which if removed would lead to one’s falling, however, sleeping in a standing or sitting position without any kind of prop, or in the prescribed Sunnat positions of Ruku or Sajda will not break wudu.”
Ala’ al-Din Abidin, the son of Ibn Abidin, explains in his Gifts of Guidance:
“Rirtual ablution is invalidated by…
The sleep of one whose rear is not firmly seated. As for the one whose rear is firmly seated, his ablution is not nullified by sleep, even if leaning against something in a way that if it were removed he would fall.”
In Talimul Haq: “If males fall asleep in the position of sajdah, but do not topple over, wudhu is not broken. However, if women fall asleep in the position of sajdah, wudu will break.”
This is because the condition for not breaking wudu in prostration is for their sujud to be according to the sunna for men (forehands off the ground, away from the body, stomach away from the thighs), as mentioned in Radd al-Muhtar, because it being so is a sign that one has effective control over one’s muscles and that they haven’t relaxed (which is what leads to gas coming out in sleep). This does not apply, of course, if women prostrate in the way that is recommended for them, with forehands on the ground and body bunched-up.