Hammad said: I asked Sa'id bin Jubayr (may Allah have mercy on him) about this saying of Allah, "And do not marry polytheist women until they believe" [Surah al-Baqarah: 221], and he said: "The idol-worshippers."
Imam al-Shafi'i (may Allah have mercy on him) said: It has been said that this verse was revealed concerning all the polytheists; then a special permission was given regarding the free women of the People of the Book, just as the slaughtered animals of the People of the Book were declared lawful. Allah says: "This day all good things have been made lawful for you. The food of those who were given the Scripture is lawful for you, and your food is lawful for them. And (lawful for you are) chaste women from among the believers and chaste women from among those who were given the Scripture before you, when you have given them their bridal dues." [Surah al-Ma'idah: 5]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13975