First of all, we’d like to state that a Muslim must fear Allah and keep from deviating from the right path by observing the fast of Ramadan and keeping away from major and minor sins in this sacred month. One must have the ability to resist one’s desires, for whoever is defeated by hunger or desire can never be victorious. The month of Ramadan is a blessed month and an opportunity for every Muslim to draw near to Allah, increase his morality and spirituality, and to gain abundant reward rather than violating its sanctity.
Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states: To commit a major sin in Ramadan is a double sin: the sin of breaking the sanctity of Ramadan and breaking the fast as well as the sin of transgressing the limits of Allah. So anyone guilty of such a sin must immediately return to Allah in repentance and do expiatory measures in order to seek Allah’s forgiveness and pardon.

Now coming to the precise method of atoning or expiating for this grievous offense, a Muslim needs to do the following:
First, he must repent sincerely, which involves showing deep remorse for committing a grave offense, refraining from such sins altogether, staying away also from such deeds or circumstances that may lead him into such sins, and, finally, resolving never to do it again and then occupying himself with good deeds as much as possible.
Second, one should offer a kaffarah (expiation): We read in the authentic Hadith that a person who broke the fast of Ramadan by having sexual intercourse with his wife was ordered by the Prophet (peace and blessings be upon him) to fast two months consecutively; when the person told him that he wouldn’t be able to do that, he was ordered to feed sixty poor persons. According to scholars, this rule must also apply to anyone who breaks the fast through illicit sexual relations as well.
Third, one must make up for the fast he has thus broken.
May Allah make us hate sins and everything that brings us closer to them, and may He make us love righteousness and piety and remain steadfast in them. Ameen.