Musannaf Ibn Abi Shayba 13:1183

Abu Bakr narrated to us, he said: Abu Dawud al-Tayalisi narrated to us, from Shu'bah, he said: Khalid ibn Abi al-Salt informed me, he said: Umar ibn Abd al-Aziz said to me: Umar ibn al-Khattab decreed regarding the child of adultery that his master is to be compensated [for the child's value] by the service he performed, and whatever remains, he is enriched by it. And I have decreed that he is to be compensated by the service he performed, and whatever remains, I have paid it on his behalf from the public treasury (Bayt al-Mal).