Q: What are the reasons annexed to the second commandment?
A: The reasons annexed to the second commandment are, God's sovereignty over us, his propriety in us, and the zeal he hath to his own worship.

Psalm 95:2-3. Let us come before his presence with thanksgiving, and make a joyful noise unto him with psalms. For the LORD is a great God, and a great King above all gods.
Psalm 45:11. So shall the king greatly desire thy beauty: for he is thy Lord; and worship thou him.
Exodus 34:14. For thou shalt worship no other god: for the LORD, whose name is Jealous, is a jealous God.

Westminster Project - See Matthew Henry's Scripture Catechism based on the WSC