Ikrimah (may Allah have mercy on him) narrates from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both): "So eat of that over which the name of Allah has been mentioned" [Surah al-An'am: 118], "And do not eat of that over which the name of Allah has not been mentioned" [Surah al-An'am: 121]. But He made an exception to it: "And the food of those who were given the Scripture is lawful for you, and your food is lawful for them" [Surah al-Ma'idah: 5].
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19153