whoever is overcome by desire and has sexual intercourse with his wife when she is menstruating and before she becomes clean must give the value of one dinar's weight of gold or about 4.25 grams (4.2315 to be more precise), or half that amount. this is based on a hadith narrated by 'abdullaah ibn 'abbaas from the prophet in relation to one who enters his wife while she is on her period as follows: "let him give one dinar in charity, or one half dinar." [at-tirmidhee, abu dawood, at-tabaraani and others: saheeh].