The World Federation One Stop Fiqh

Ruling 450

If a man has sexual intercourse with his wife while she is in the state of ḥayḍ, it is obligatory for him to seek forgiveness from Allah. However, giving recompense (kaffārah) is not obligatory for him, even though it is better that he give kaffārah. The kaffārah for sexual intercourse at the beginning of ḥayḍ is one legal (sharʿī) mithqāl48 of coined gold, at the middle of ḥayḍ it is half a legal mithqāl, and at the end of ḥayḍ it is one quarter of a legal mithqāl. A legal mithqāl is eighteen nukhuds.49

48 A legal mithqāl is a measure of weight equal to 3.456 grams.
49 A nukhud is a measure of weight equivalent to 0.192 grams.