Paul here combines various OT passages such as Isa. 52:11-12; Jer. 51:6, 45. The historical reference is to the departure of captive Israelites from ancient Babylon, which Paul here refers to as an illustration of the separation of God’s people from the world and from spiritual Babylon (see on Rev. 18:4). Upon their return from captivity the Jews were charged not to carry back with them anything savoring of pagan idolatry. Similarly, spiritual Israel is charged to “touch not the unclean thing” (see on Isa. 52:11, 12).