The sin of idolatry, condemned by our Lord in the Gospel today, begins in the overweening concern for things, for money, for other persons. Any person, place or thing which we admit to first place in our lives becomes an idol, for the first place in our hearts, mind and souls belongs to God alone.
Idolatry not only refers to false pagan worship. It remains a constant temptation to faith. Idolatry consists in divinising what is not God. Man commits idolatry whenever he honours and reveres a creature in place of God, whether this be gods or demons (for example, satanism), power, pleasure, race, ancestors, the state, money, etc. Jesus says, "You cannot serve God and mammon." (Matthew 6:24) Many martyrs died for not adoring "the Beast" (Cf. Revelation 13-14) refusing even to simulate such worship. Idolatry rejects the unique Lordship of God; it is therefore incompatible with communion with God." (Origen, Contra Celsum 2, 40: PG 11, 861.) (CCC 2113)
The Lord gives us a practical rule of life in order that we may successfully avoid the sin of idolatry while at the same time living in harmony with the beauty of creation and having our natural needs fulfilled: "Seek first the kingdom of God and his service and all these things will be given you as well.' (Matthew 6, 33)
Human life finds its unity in the adoration of the one God. The commandment to worship the Lord alone integrates man and saves him from an endless disintegration. Idolatry is a perversion of man's innate religious sense. An idolater is someone who "transfers his indestructible notion of God to anything other than God." (CCC 2114).
Not only our spiritual integrity and eternity depends upon the true worship of the true God, but our sanity and worldly happiness as well.