What does the Bible mean when it states that God is a “jealous” God?

How to worship the true God is found in the Ten Commandments. Exodus 20, verses 4-6 state, “You shall not make unto you any graven image, or any likeness of any thing that is in heaven above, or that is in the earth beneath, or that is in the water under the earth: You shall not bow down yourself to them, nor serve them: for I the Lord your God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate Me; And showing mercy unto thousands of them that love Me, and keep My commandments.” This is repeated in Deuteronomy 5:8-10.

The Hebrew word qanna is used here and means “jealous.” To gain the proper sense of this word, the best definition is “exacting exclusive devotion; intolerant of rivalry” (Webster’s New International Dictionary, 2nd Edition, 1954). In other places, the Hebrew word qana is used, which mean “zealous.” This is defined as “Filled with, characterized by, or due to zeal; warmly engaged, or ardent, esp. in behalf of an object; zealous service.

The moment any man sets up any image or representation of God, he is breaking the second commandment—thus denigrating God’s status and power. They not only hurt themselves, but their false worship will cause hurt to their children and grandchildren as well. But together with this warning is a promise. Those who worship the true God—the way He commands—are shown mercy “unto thousands of them that love Me.”