Does sleep in which one is unaware of its depth nullify ablution?

If a sleeping person doubts whether their sleep nullifies their ablution or not, their ablution is not nullified by doubt. This is because the original state is the continuity of ablution until one is certain that something has occurred to nullify it. The proof for this is the Prophet, peace and blessings be upon him, who said: "He should not leave (his prayer) until he hears a sound or perceives a smell."

Therefore, whoever is certain of their ritual purity but doubts the occurrence of an impurity remains in their state of purity. This is the view of the majority of scholars. There is no difference in doubt whether the two possibilities are equal, or one is more likely, or there is strong conjecture; ablution is not required of him in any case, and it is recommended for him to perform ablution as a precaution.