The Literal Commandment
If your brother, your mother's son, or your son or daughter, or the wife you cherish, or your friend who is as your own soul, entice you secretly, saying, 'Let us go and serve other gods' (whom neither you nor your fathers have known, of the gods of the peoples who are around you, near you or far from you, from one end of the earth to the other end), you shall not yield to him or listen to him; and your eye shall not pity him, nor shall you spare or conceal him. (Deuteronomy 13:6-8)
The literal commandment is that we should not spare a person who attempts to entice us into idolatry.
We should not spare them from what? From the death penalty proscribed for their offense (Deuteronomy 13:9).