Paul is going to use a startling example to teach the meaning of “idolatry”: The nation of Israel and its calling by God through Moses. The point harkens back to Paul’s teaching in 1 Corinthians 8:1-3 that a relationship with the One True God subsists in love, not knowledge or ritual.
“Now concerning things sacrificed to idols, we know that we all have knowledge. Knowledge makes arrogant, but love edifies. If anyone supposes that he knows anything, he has not yet known as he ought to know; but if anyone loves God, he is known by Him.”
– 1 Corinthians 8:1-3
Like the false religions of their day, the Israelites took the holy things entrusted to them by God and treated them merely as rituals and rules just like the worship of any other idol. The question for us is whether we’re doing the very same thing with the Gospel and gifts provided to us. It’s about the quality of our relationship with Christ, not the service in and of itself.