C.J. Mahaney in his book, The Cross Centered Life, provides two quotes that tie his topic to the issue of idolatry:

I fear that the cross, without ever being disowned, is constantly in danger of being dismissed from the central place it must enjoy, by relatively peripheral insights that take on far too much weight.  Whenever the periphery is in danger of displacing the center, we are not far removed from idolatry. – D. A. Carson

Legalism has its origin in self-worship. [i.e. idolatry]  If people are justified through their obedience to the law, then they merit praise, honor, and glory.  Legalism, in other words, means the glory goes to people rather than God. – Thomas Schreiner

(For more thoughts on idolatry, see the new Three Passions Idolatry page.)