Reference: Fataawa Ramadhaan – Volume 2, Page 440, Fatwa No.364
Fataawa Ibn ‘Uthaymeen – Volume 1, Page 524
Question: Regarding the one who [was fasting and] had a wet dream during the day in Ramadhaan?
Response: Regarding that, we say his fast is sound and correct. Certainly, a wet dream does not invalidate the fast because it occurred without his own choice. And the pen [for recording one’s deeds] has been raised whilst he is sleeping. However, it is befitting the person occupies himself during the fasting day with the remembrance of Allaah, reciting the Qur.aan and [other] acts of obedience to Allaah (Subhaanauhu wa Ta’aala), and not to do as many of the people do by idly remaining awake during the night in Ramadhaan engaging in acts which do not benefit them, rather, harms them. And during the day, they spend the entire day asleep, and this is not befitting. Rather, what is befitting for the person to do is to make his fasting a time for obedience, remembrance [of Allaah], reciting the Qur.aan and other than these [acts] from that which bring one closer to Allaah (Tabaarak wa Ta’aala). And Allaah has the complete knowledge.