For the Lord your God is a consuming fire, a jealous God. Deuteronomy 4:24
Jealousy is an ugly word. “It is the green-eyed monster,” said Shakespeare in Othello. It has overtones of selfishness, suspicion, and distrust, and implies a hideous resentment or hostility toward other people because they enjoy some advantage. It is possessive, demanding, and overbearing; and that is repulsive. It stifles freedom and individuality, it degrades and demeans, it breeds tension and discord, it destroys friendships and marriages. We view jealousy as a horrible trait and we hate it. If all of this is true, why is God called a "jealous God?"
God is not jealous in an insecure, human way. God is jealous in that God has claimed us as his own and he will not share us with idols. This is holy love. See also Deut. 5: 9
God is passionate about his relationship with you and will not share you with another. This is why Scripture says the Lord is God. God will not take second place in our lives.