Have I committed a sin by the involuntary emission of semen after swearing on the Qur'an to abandon masturbation for two months?

Scholars differed on whether the emission of semen merely by looking constitutes masturbation or not. The Shafi'is and Malikis held that masturbation occurs through looking, and it invalidates the fast according to them. As for the Hanbalis, the fast is invalidated for them if looking is repeated. The Hanafis disagreed with them, stating that it does not break the fast of the fasting person at all, and this is the relied-upon opinion among the Shafi'is. It is safer to consider it masturbation, and in this case, an expiation for a broken oath (kaffarat yamin) is due. If it is not considered masturbation, then there is no expiation, but watching forbidden things is a sin from which one must repent.