A Wet Dream Does Not Break the Fast, but Intercourse Does
Question
If someone is fasting and in his sleep ghusl becomes necessary for him, or he knowingly and deliberately has intercourse, will the fast remain or not? And if it remains, in what state?
Answer
The fast is not broken by a wet dream (ihtilam). However, it is broken by deliberate intercourse, and kaffara (expiation) and qada (make-up) become binding upon the person. If it is a fast other than that of Ramadan, only qada will be obligatory, and kaffara will not be obligatory.
Source: Fatawa Mahmudiyya
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