Some do not perceive the differences between the first and second commandments. However, the first stresses the uniqueness, the matchless distinctiveness of the Creator God. It draws attention to our obligation to the One without whom there would be no life or hope at all. He is also the Source of truth, right values, and standards that will produce right relationships and peaceful prosperity so that life is not merely lived but has the potential to contain great peace, joy, and accomplishment. Thus, the first commandment deals with what we worship.
In contrast, the second commandment covers the way we worship. The Father and Son are unique Individuals who come into our lives from beyond this physical realm. They are absolutely holy, pure, and undefiled, uncreated and eternal. An idol, on the other hand, is someone or something of any other realm that we make and value, giving it devotion that rightfully belongs to the Creator.
John 4:24 instructs us regarding the way God desires that we worship Him: "God is Spirit, and those who worship Him must worship in spirit and in truth." The second commandment regulates a specific area of idolatry; it deals with God's spirituality. It thus involves our manner of worship in faith, most obviously in that it prohibits the use of physical "helps" or "aids" in worshipping the invisible, spiritual God.
Take careful heed to yourselves, for you saw no form when the LORD spoke to you at Horeb out of the midst of the fire, lest you act corruptly and make for yourselves a carved image in the form of any figure: the likeness of male or female.
Since no one has ever seen God, whatever is made to picture Him would be a work of man's hands and a lie. It is helpful to recall that the Holy of Holies contained no representation of God. The Bible frequently uses the image of an altar to indicate the worship of God, yet, except for the Temple's brazen altar, even they were to be made of simple turf or uncut stones (Exodus 20:22-26). Additionally, the second commandment prohibits the use of anything that represents God or could become an object of veneration. Thus, it prohibits any kind of likeness of Christ such as crucifixes, pictures, and statues.
Numbers 33:52 commands the Israelites, ". . . then you shall drive out all the inhabitants of the land from before you, destroy all their engraved stones, destroy all their molded images, and demolish all their high places. . . ." This destruction was not to be wanton, but God intended it to involve only religious, worshipped things. Why?
Any representation of God changes Him into a different god from what He really is. Egypt, from whence Israel came, worshipped oxen, heifers, sheep, goats, lions, dogs, cats, monkeys, ibis, crane, hawks, crocodiles, serpents, frogs, flies, beetles, sun, moon, planets, stars, fire, light, air, and darkness. Very likely, an Egyptian could come up with "good" reasons why he did so. A man wrote in an email that he did not care whether the Bible said not to worship as the pagans do through the use of Christmas and Easter. He was going to do it anyway because it was his way of praising God. He is worshipping a god of his own design.
Idolatry, then, denies the true nature of God, so obedience to this commandment determines the way we worship. It must be in spirit and in harmony with His nature, which the Bible reveals. Knowing God's true nature is important because we become what we worship. Thus, this commandment covers idolatry in a form in which the true God is worshipped through either a false image or a corrupt practice. This false representation perverts His reality. If we idolize, we become the wrong thing.