He Is Jealous For Me.
you shall not bow down to them nor serve them. For I, the Lord your God, am a jealous God, visiting the iniquity of the fathers upon the children to the third and fourth generations of those who hate Me. Exodus 20:5 NKJV
The second commandment concerns the ordinances of worship, or the way in which God will be worshiped, which it is fit that he himself should have the appointing of. Here is,
The prohibition: we are here forbidden to worship even the true God by images. The Jews (at least after the captivity) thought themselves forbidden by this commandment to make any image or picture whatsoever. Hence the very images which the Roman armies had in their ensigns are called an abomination to them (Matthew 24:15), especially when they were set up in the holy place. It is certain that it forbids making any image of God (for to whom can we liken him? Isaiah 40:15,18), or the image of any creature for a religious use. It is called the changing of the truth of God into a lie (Romans 1:25), for an image is a teacher of lies it insinuates to us that God has a body, whereas he is an infinite spirit, Habakkuk 2:18. It also forbids us to make images of God in our fancies, as if he were a man as we are. Our religious worship must be governed by the power of faith, not by the power of imagination. They must not make such images or pictures as the heathen worshiped, lest they also should be tempted to worship them. Those who would be kept from sin must keep themselves from the occasions of it. They must not bow down to them occasionally, that is, show any sign of respect or honour to them, much less serve them constantly, by sacrifice or incense, or any other act of religious worship. When they paid their devotion to the true God, they must not have any image before them, for the directing, exciting, or assisting of their devotion. Though the worship was designed to terminate in God, it would not please him if it came to him through an image. The best and most ancient lawgivers among the heathen forbade the setting up of images in their temples. This practice was forbidden in Rome by Numa, a pagan prince yet commanded in Rome by the pope, a Christian bishop, but, in this, anti-christian. The use of images in the church of Rome, at this day, is so plainly contrary to the letter of this command, and so impossible to be reconciled to it, that in all their catechisms and books of devotion, which they put into the hands of the people, they leave out this commandment, joining the reason of it to the first and so the third commandment they call the second, the fourth the third. Only, to make up the number ten, they divide the tenth into two. Thus have they committed two great evils, in which they persist, and from which they hate to be reformed they take away from God's word, and add to his worship.
The reasons to enforce this prohibition, which are, God's jealousy in the matters of his worship: "I am the Lord Jehovah, and thy God, am a jealous God, especially in things of this nature." This intimates the care he has of his own institutions, his hatred of idolatry and all false worship, his displeasure against idolaters, and that he resents every thing in his worship that looks like, or leads to, idolatry. Jealousy is quicksighted. Idolatry being spiritual adultery, as it is very often represented in scripture, the displeasure of God against it is fitly called jealousy. If God is jealous herein, we should be so, afraid of offering any worship to God otherwise than as he has appointed in his word.
The punishment of idolaters. God looks upon them as haters of him, though they perhaps pretend love to him he will visit their iniquity, that is, he will very severely punish it, not only as a breach of his law, but as an affront to his majesty, a violation of the covenant, and a blow at the root of all religion. He will visit it upon the children, that is, this being a sin for which churches shall be unchurched and a bill of divorce given them, the children shall be cast out of covenant and communion together with the parents, as with the parents the children were at first taken in. Or he will bring such judgments upon a people as shall be the total ruin of families. If idolaters live to be old, so as to see their children of the third or fourth generation, it shall be the vexation of their eyes, and the breaking of their hearts, to see them fall by the sword, carried captive, and enslaved. Nor is it an unrighteous thing with God (if the parents died in their iniquity, and the children tread in their steps, and keep up false worships, because they received them by tradition from their fathers), when the measure is full, and God comes by his judgments to reckon with them, to bring into the account the idolatries their fathers were guilty of. Though he bear long with an idolatrous people, he will not bear always, but by the fourth generation, at furthest, he will begin to visit. Children are dear to their parents therefore, to deter men from idolatry, and to show how much God is displeased with it, not only a brand of infamy is by it entailed upon families, but the judgments of God may for it be executed upon the poor children when the parents are dead and gone. - Matthew Henry