Reference: Fataawa Ramadhaan v2 p440 no.365
al-Muntaqaa min Fataawa ash-Shaykh Saalih ibn Fowzaan v3 p162
Question: If one who is fasting has a wet dream during the day in Ramadhaan, does this nullify his fast or not and should he perform the ritual purification [of ghusl]?
Response: If one who is fasting has had a wet dream during the day in Ramadhaan, then his fast is sound and is not affected by the wet dream, because he had not done so intentionally. However, it is obligatory for him to perform the ritual purification (ghusl) so as to perform the prayer. To be prompt in performing the ritual purification is better, but not obligatory.
And Allaah [alone] has the Complete knowledge [of all affairs].
