From the Shorter Catechism
Q. 49. Which is the second commandment?
A. The second commandment is, Thou shalt not make unto thee any graven image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth; thou shalt not bow down thyself to them, nor serve them; for I the Lord thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me: and showing mercy unto thousands of them that love me, and keep my commandments. Ex. 20:4-6.