God frequently cites His jealousy as His motivation for acting in the OT. His jealousy causes Him to judge and it also causes Him to show mercy. His name is at stake.
God loves His people: He is their God and they are His people. He is bound up with them and thus becomes jealous, not merely because of who they are, but because He is jealous for His own name.
Israel is a great illustration for us, the things that happened to them were written for our learning so we might not repeat the same stupid steps.
God was jealous over Israel because He dwelt among them, He put His name on them and revealed Himself to the nations through them. Yet they threw it away, trampled His name under foot and became like the nations.
This did not go over well. Today all believers have become the temple of the Holy Spirit and God has put His name on us and His Spirit in us. Can we then assume that God is jealous for us? Oh yeah!
Or do you suppose it is to no purpose that the Scripture says, “He yearns jealously over the spirit that he has made to dwell in us“?
God is jealous over us because we have His Spirit, thus He infinitely cares what we do while possessing Him. We are the temple, what fellowship has light with darkness? Come out from among them and be separate.
The Spirit in us not only brings power and life, it brings responsibility. Indeed we ought to tremble at the very notion of God dwelling in us. What a privilege, what a weight of glory!
What blessed responsibility! Let the Spirit shine and remember you’ve been bought with a price, you are not your own, so glorify God in your body.