Musannaf Ibn Abi Shayba 9:1535

Abu Bakr narrated to us, he said: Abdullah ibn al-Mubarak narrated to us, from Isma'il, the freed slave of Banu Makhzum, who said: I asked 'Ata' about a woman who said to her slave, "I will free you on the condition that you marry me." He said, "If only she had begun by freeing him." He said: And I asked Abdullah ibn Ubayd ibn Umayr, and he said the same as what 'Ata' said. He said: Then I asked Mujahid, and he became angry and said, "In this is a punishment from Allah and from the authority."