If jealousy is a sin, then why does God say He is a Jealous God?
One of the verses that speaks about this is in the Ten Commandments. In the later part of verse 5 of Exodus chapter 20, it reads;
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, 6 but showing mercy to thousands, to those who love Me and keep My commandments. Ex.20:5-6
The Hebrew word for jealous (kanna) (קַנָּא) does not mean what the English word jealous means. In English, this word is in fact referring to a sin. Jealousy for something someone has, or for wanting to be like someone else.
God can never be jealous for something someone has. The context of jealous here in this scripture is saying God is a zealous God. That is He has a zeal, which is strong and determined desire for His people to refrain from worshiping any other god. The above verses reveal God’s right for justice and His determination (zeal) for righteousness and intolerance for worship to any other god than other than Him.