Fasting: Masturbation
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1567
If a fasting person masturbates (the meaning of masturbation was mentioned in Ruling 1551), his fast becomes invalid.
Ruling 1568
If a person ejaculates involuntarily, his fast does not become invalid.
Ruling 1569
Whenever a fasting person knows that if he goes to sleep during the day he will have a wet dream [i.e. become muḥtalim] – meaning that semen will be ejaculated in his sleep – it is permitted (jāʾiz) for him to go to sleep even if he will not encounter difficulty by not sleeping; and if he has a wet dream, his fast does not become invalid.
Ruling 1570
If a fasting person wakes up from sleep while ejaculation is taking place, it is not obligatory for him to stop the ejaculation.
Ruling 1571
A fasting person who has a wet dream can urinate even if he knows that by urinating, some of the remaining semen will come out of his penis.
Ruling 1572
If a fasting person who has a wet dream knows that some semen has remained in his penis, and he knows that if he does not urinate before performing ritual bathing (ghusl), semen will be discharged after ghusl, then the recommended precaution is that he should urinate before performing ghusl.
Ruling 1573
If someone intentionally indulges in courtship with the intention of ejaculating but does not ejaculate, and he does not make another intention to fast, his fast is invalid. If he does make another intention to fast, then based on obligatory precaution, he must complete his fast and keep a qaḍāʾ fast as well.
Ruling 1574
If, for example, a fasting person indulges in courtship with his wife without the intention of ejaculating, in the event that he is confident [i.e. he has iṭmiʾnān] that he will not ejaculate but does ejaculate, his fast is valid. However, if he is not confident that he will not ejaculate and does ejaculate, his fast is invalid.