Q: What is the preface to the ten commandments?
A: The preface to the ten commandments is in these words, I am the Lord thy God, which have brought thee out of the land of Egypt, out of the house of bondage.

Q: What doth the preface to the ten commandments teach us?
A: The preface to the ten commandments teacheth us, That because God is the Lord, and our God, and Redeemer, therefore we are bound to keep all his commandments.

Q: Which is the first commandment?
A: The first commandment is, Thou shalt have no other gods before me.

Q: What is required in the first commandment?
A: The first commandment requireth us to know and acknowledge God to be the only true God, and our God, and to worship and glorify him accordingly.

Q: What is forbidden in the first commandment?
A: The first commandment forbiddeth the denying, or not worshipping and glorifying the true God as God, and our God; and the giving of that worship and glory to any other, which is due to him alone.

Q: What are specially taught by these words before me in the first commandment?
A: These words before me in the first commandment teach us, That God, who seeth all things, taketh notice of, and is much displeased with, the sin of having any other god.

(Questions XLIII, XLIV, XLV, XLVI, XLVII and XLVIII from the Westminster Shorter Catechism)