Likewise, among the acts that invalidate the fast is removing a large quantity of blood by ḥijāmah (cupping), faṣd (venesection), or drawing blood to donate or to aid a patient. This too breaks the fast and obligates making up that day, for the Prophet (peace and blessings be upon him) said, “The cupper and the one being cupped have broken the fast.” Therefore, whoever undergoes any of these procedures has voided his fast and must compensate for that day.

There are, however, other matters that are forbidden for the fasting person and that diminish—or even wipe out—his reward, yet they do not require him to repeat the fast. These include backbiting, tale-bearing, false testimony, insulting others, lying, and similar sins.

The same ruling applies to forbidden glances and to listening to unlawful things such as idle entertainment, songs, and musical instruments. All of these negatively affect the fast by reducing or nullifying its reward, but they do not necessitate making up the day, because they are intangible invalidators rather than physical ones.

Wet Dream During the Daytime Fast
Question: What is the ruling on someone who experiences a wet dream while fasting during the day? Does it affect the validity of his fast?

Answer: If a person has a wet dream during the daytime of the fast, he must perform ghusl (the ritual bath for major impurity). As for his fast, it remains valid, because a wet dream occurs without one’s choice or intent; it simply happens.