Musnad Ahmad 25:194

Yahya narrated to us, from Shu'bah, and Muhammad ibn Ja'far, Shu'bah narrated to us, from al-Hakam, from 'Abd al-Hamid ibn 'Abd al-Rahman, from Miqsam, from Ibn 'Abbas, from the Prophet, may Allah bless him and grant him peace, regarding the one who comes to his wife while she is menstruating: "He shall give in charity a dinar, or half a dinar." 'Abdullah said: My father said: 'Abd al-Rahman did not attribute it to the Prophet (marfu'), nor did Bahz.