"You shall have no other gods before Me" (Exodus 20:3).
OUR CREATOR IS THE ONLY BEING WHOM WE MAY WORSHIP, AND WE MUST MAKE IT OUR AIM TO WORSHIP HIM AS HE TRULY IS. God is the only eternal, self-existent Being. Of all the things that exist, only He is uncreated -- everything else that exists has been caused to exist by Him. Hence, if we worship anything other than God, we are worshiping a created thing, a "creature," rather than the Creator, who alone is to be worshiped (Romans 1:20-25).
The Scriptures have a good deal to say about the danger of "idolatry." But is it really the practical problem today that it was in ancient times? We probably don't feel much temptation to worship anything in nature, and we certainly wouldn't make a graven image. If we're concerned about idols at all, we're probably more tempted by the modern ones like money and material things (Colossians 3:5). But whether the idolatry is ancient or modern, we don't see it as a serious problem because we are people who know that God should be our highest concern.
But suppose we've enthroned God in our hearts, and the thing that occupies the throne is simply a false conception of Him. Suppose the "God" we worship is not God as He has revealed Himself to be, but God as we have wrongly conceived Him in our own minds. In this case, are we not worshiping a "creature" of our own making? And are we not practicing a form of idolatry that is all the more dangerous because it is so subtle and sophisticated?
These days there seems to be a growing tendency for us to define God in the subjective terms of our own likes and dislikes. We demand that God be the kind of God we think He should be, or else we won't "believe" in Him. But we'd better be careful. A day is coming when our very real Creator will be our very real Judge. If we've been unwilling to bow before the awesome truth of His reality and have concocted an imaginary "God" more agreeable to us, then the real God, the Reality that we found so unacceptable in time, will simply be unavailable to us in eternity.
"Let us beware lest we in our pride accept the erroneous notion that idolatry consists only in kneeling before visible objects of adoration, and that civilized peoples are therefore free from it. The essence of idolatry is the entertainment of thoughts about God that are unworthy of Him. It begins in the mind and may be present where no overt act of worship has taken place" (A. W. Tozer).