The second most serious sin that breaks the fast is masturbation. This we get from the hadith of Prophet Muhammad (peace be upon him),“Prophet said that Allah subhanwatala said ‘all the deeds of son of Adam are for himself except for fasting it is for me and I will reward it. The person he abstains from eating, drinking and his desires for my sake’…” So this desire from where we come to know it includes doing masturbation. So when a person masturbates or ejaculates whether by touching his wife or looking at his wife or due to other reason or looking at any other woman. If the ejaculation takes place then the fast gets invalidated. He has to repent to Allah subhanwatala and complete that day of fasting and he should compensate for this fast, keep this fast later when Ramadan gets over. But here there is no Kaffara, there is no penalty. Because that penalty is only for sexual intercourse. Furthermore if a person does not ejaculate and if there is only ‘madhi’ that comes out – fluid. Then the fast does not break. Similarly this is a prostatic fluid (the madhi) and if this white fluid that may come out after urination then the fast does not break. Only thing he has to do is ‘istinja’ i.e. wash his private parts and do wudhu.
