God is not jealous of anything, He is God, but He is jealous for something.  God is jealous for everything He created; it is His and belongs to Him.  Specifically God is jealous for us, for our love, our time, our devotion and ultimately us.  Why you ask, because of His infinite love for us.

Spend some time reflecting on what it means that God is jealous for you.

Discuss the difference between being jealous ‘of’ and being jealous ‘for’?