The 9th & 10th commandments, the ones about coveting, are redundant. God already covered that stuff in the 6th & 7th commandments. He repeats Himself to show that sin is more than just an action. Sinful hearts desire sinful things. God shows us this because we try to dress up our thoughts with nice excuses and flowery language. The 9th and 10th commandments call us to see the depth of our sin, and then look to a savior who died for us.