What is the ruling regarding one who thought about leaving Islam and doubted it during a severe illness, and returned to his normal state after recovery?

The whispers (waswas) that a person does not utter are not held against them, whether they are conscious or unconscious of them, based on the hadith: "Indeed, Allah has overlooked for my Ummah what they whisper to themselves, as long as they do not speak of it or act upon it." And if a person dislikes these whispers, then that is a clear sign of faith.

Whoever is afflicted with whispers should disregard them. If they overcome him, accompanied by his dislike of them, then there is no sin upon him. This applies, even more so, to a sick person who has lost his mind.

And if a person afflicted with whispers speaks what he whispers to himself while in a diseased state where he does not comprehend what he is saying, he is also not held accountable, based on the hadith: "The pen has been lifted from three: from the sleeper until he awakens, from the child until he reaches maturity, and from the insane person until he regains his sanity or recovers."