The command may be translated, “stop being [or “becoming”] idolaters,” implying that some of the Israelites lapsed into idolatry.
Idolaters.
This is primarily a reference to the worship of the golden calf by the people while Moses was in the mount with God (see Ex. 32:1-5). The warning was particularly appropriate for the Corinthians, some of whom apparently felt free to attend feasts in idol temples (see on 1 Cor. 8:10; cf. ch. 10:20, 21).
The quotation is from Ex. 32:6. The Israelites at Mt. Sinai had not forgotten the things they had seen and practiced in Egypt, where idolatry was the state religion. They were well acquainted with the sensual, passionate performances that were associated with the worship of false gods, and they doubtless imitated them at the worship of the golden calf. Feasting and drinking beclouded the mind, so that men were no longer able to discern between good and evil, and they were enslaved by bodily passions, thus exposing themselves to the subtle temptations of the enemy.