Musannaf Ibn Abi Shayba 13:1995

Abu Bakr narrated to us, he said: Al-Fadl ibn Dukayn narrated to us, from Yusuf ibn al-Muhajir, he said: The Ispahbad gifted forty thousand, or less or more, to Abd al-Hamid. So he wrote to Umar ibn Abd al-Aziz. He wrote back to him: "If he was gifting it to you while you were in al-Jazira, then accept it from him; otherwise, count it for him against his land tax (kharaj)."