The Prophet (may Allah's peace and blessings be upon him) was reported to have said concerning a man who engages in sexual intercourse with his wife during her menses: Let him give one dinar or half a dinar in charity
Authentic hadithعن ابن عباس رضي الله عنهما ، عن النبي صلى الله عليه وسلم في الذي يأتي امرأته وهي حائض قال: «يتصدق بدينار أو نصف دينار».
Ibn ‘Abbās (may Allah's peace and blessings be upon him) reported: The Prophet (may Allah's peace and blessings be upon him) said concerning a man who engages in sexual intercourse with his wife during her menses: "Let him give one dinar or half a dinar in charity."
Explanation
In this Hadīth, the Messenger of Allah (may Allah's peace and blessings be upon him) clarifies the expiation due on someone who engages in sexual intercourse with his wife while she is menstruating. The expiation is to pay a dinar or half a dinar in charity. We learn from the Hadīth that having sexual intercourse with a woman during her menstruation is prohibited, because it results in expiation. The Hadīth also serves as evidence of the obligation of giving in charity, because it is done as a compensation for a sin.
Source · Narrated by Ibn Majah - An-Nasaa’i - Narrated by Abu Daoud - Narrated by Ahmad - Ad-Daarimi
From the Hadith Encyclopedia (hadeethenc.com).