Musannaf Ibn Abi Shayba 9:294

Affan narrated to us, he said: Hammad bin Salamah narrated to us, from Ata’ bin al-Sa’ib, from Ikrimah, from Ibn Abbas, he said: Eat the slaughtered animals of the Banu Tha’lab and marry their women, for Allah the Exalted says: "O you who have believed, do not take the Jews and the Christians as allies. They are [in fact] allies of one another." If they were not among them except by [the act of] alliance, then they would be among them.