Westminster Larger Catechism

Q114

What reasons are annexed to the third commandment?

The reasons annexed to the third commandment, in these words, The Lord thy God, and, For the Lord will not hold him guiltless that taketh his name in vain,617 are, because he is the Lord and our God, therefore his name is not to be profaned, or any way abused by us;618 especially because he will be so far from acquitting and sparing the transgressors of this commandment, as that he will not suffer them to escape his righteous judgment;619 albeit many such escape the censures and punishments of men.620
Duty