Exodus 34:14
14 For thou shalt worship no other god: for the LORD, whose name is Jealous, is a jealous God:
This is pretty simple, God does not want only half of your attention, he wants it all. God does not want you to only serve him on Sundays, God wants you to serve him 24/7. God is jealous when we give other things the attention we should be giving him. He is jealous whenever we put things before him. I for one do not want God, who can destroy nations, to be jealous of something I have placed before him. Put God first in your life, so that he never has to be jealous.
Warrior's Word of Faith 