It was narrated from Ibn 'Abbas from the Prophet (ﷺ) concerning a man who has had intercourse while she was menstruating:
"Let him give a Dinar or half a Dinar in charity." (JA)
English reference (JA): Vol. 1, Book 1, Hadith 290 (JA)
Arabic reference (JA): Book 1, Hadith 291 (JA)