Now and then people ask what the Bible means when it says God is jealous. For instance, Exodus 20 declares, “the LORD your God is a jealous God, visiting iniquity upon the wicked.” Since God is incapable of sin, what do these texts mean? I think the answer will not only help you understand but even appreciate the Bible’s description of our “jealous” God. But first, let’s get something clear about the words we use to describe God.
Analogical Language
God is uncreated and transcendently wonderful. His perfections infinitely exceed the experience and comprehension possible to creatures. For that reason, when the Bible sets out to describe the Lord’s nature and attributes, it cannot do so comprehensively. There are simply no human words to fully convey his glorious being. Instead, it uses what we might call "analogical" language. That is, it speaks truthfully in ways accommodated to our finite comprehension by employing metaphors and analogies based on created things humans can relate to. God’s providence is described as a mighty hand. His omniscience is likened to eyes. Even exact descriptions, such as “the Lord is faithful,” rely upon a human conception of faithfulness that falls short of the infinitude of God’s faithfulness.
Analogies about God necessarily fall short but that doesn't mean they are useless. For instance, if I was trying to explain the taste of coffee to someone who had never tasted it, I might say, "it's a brewed beverage somewhat like tea but stronger and nuttier." Anyone who has tasted both coffee and tea might object that the two are very different, and they are in comparison to one another. But to the one who has only tasted tea, the analogy prevents them from imagining coffee to be anything like milk, beer, or wine. It puts them in the ballpark for conceiving of the thing in question. Even so, human descriptions of God will always fall short of the divine realities which they signify, but they help bring us closer to understanding who he is.
How is God jealous?
Now, back to the word "jealousy." Obviously, God is sinless. Therefore, whatever is communicated by the term. “jealousy” must not signify any fault within the divine being. Sadly, as sinners, our best feelings are tinged with sin and selfishness and jealousy is no exception. Our experience of that feeling is typically intermixed with pettiness, envy, and distrust. But in God's case, "jealousy" represents only the purest motives and feelings connected with the term.
By way of illustration, suppose a wife discovers her husband has been cheating on her. Jealousy in this case is not entirely unwarranted or sinful. Rather, feelings of disappointment, grief, and wrath work together in this instance to manifest the wife’s high regard for marriage itself, as well as for their mutual commitment and her own personal dignity, all of which are slighted by adultery. For the wife to be entirely without jealousy would imply a sinful indifference to the sanctity of marriage and the evil of adultery. Therefore we can say that jealousy in its purest sense is a righteous zeal for the honor and integrity of something or someone.
Even so, God's jealousy is a pure and fervent regard both for divine honor as well as for the sacred bond he shares with believers in Christ, a relationship comparable to marriage (cf. Eph 6:1ff). For God to be without such jealousy would actually be a fault as it would mean he is indifferent to sin and idolatry. But let me add one word of advice. We must be careful not to slip lazily into thinking of God monopersonally, as the world generally does. No, as Christians, we must think of God's attributes, especially jealousy, tripersonally. That is, understanding that each Person of the Trinity is not concerned for himself so much as for the dignity of the other divine Persons. The Father is appropriately jealous for his Son to be accorded due honor. The Son is similarly jealous for his Father to be revered. The Holy Spirit is zealous for the Father and Son to be cherished and obeyed. Thinking tripersonally of God’s jealousy prevents us from collapsing divine motives into selfishness.
I hope this answer helps you to appreciate this often misunderstood aspect of God revealed in the Word. The Lord bless your studies and service!