From the Shorter Catechism
Q. 56. What is the reason annexed to the third commandment?
A. The reason annexed to the third commandment is, that however the break- ers of this commandment may escape punishment from men, yet the Lord our God will not suffer them to escape his righteous judgment. 1 Sam. 2:12, 17, 22, 29; 1 Sam. 3:13; Deut. 28:58-59.