Musannaf Ibn Abi Shayba 3:3158

Yazid ibn Harun narrated to us, he said: Hammam ibn Yahya informed us, from Qatadah, from Qudamah ibn Wabra al-’Ijli, from Samurah ibn Jundab, from the Prophet (may Allah bless him and grant him peace), he said: "Whoever leaves the Friday [prayer] without an excuse, let him give a dinar in charity. If he does not find [one], then half a dinar."