Here's some more if understanding still eludes you.
In a similar way, Jehovah expressed His love for Israel in the Old Testament by proclaiming to be “a jealous God” (Exodus 20:5; Deuteronomy 4:24). He was not envious of the Israelites’ accomplishments or possessions, but was communicating His strong love for them with anthropomorphic language. The Scriptures depict a spiritual marriage between Jehovah and His people. Sadly, during the period of the divided kingdom, both Israel and Judah were guilty of “playing the harlot” (Jeremiah 3:6-10). God called Israel’s idolatrous practice “adultery,” and for this reason He had “put her away and given her a certificate of divorce” (3:8). This is not the “lunatic fury of a rejected or supplanted suitor,” but a “zeal to protect a love-relationship” (Packer, p. 189). Jehovah felt for Israel “as the most affectionate husband could do for his spouse, and was jealous for their fidelity, because he willed their invariable happiness” (Clarke, 1996, emp. added). Song of Solomon 8:6 is further proof that love and jealousy are not always opposed to each other. To her beloved, the Shulamite said: “Put me like a seal over your heart, like a seal on your arm. For love is as strong as death, jealousy is as severe as Sheol; its flashes are flashes of fire, the very flame of the Lord” (NAS). In this passage, love and jealousy actually are paralleled to convey the same basic meaning (see Tanner, 1997, p. 158)—that (aside from one’s love for God) marital love is “the strongest, most unyielding and invincible force in human experience” (NIV Study Bible, 1985, p. 1012). In this sense, being a jealous husband or wife is a good thing. As one commentator noted, married persons “who felt no jealousy at the intrusion of a lover or an adulterer into their home would surely be lacking in moral perception; for the exclusiveness of marriage is the essence of marriage” (Tasker, 1967, p. 106).
