Westminster Shorter Catechism

Q53

Which is the third commandment?

The third commandment is, Thou shalt not take the name of the Lord thy God in vain: for the Lord will not hold him guiltless that taketh his name in vain133.
Duty
Ch. XXII Of Lawful Oaths and Vows

Scripture Proofs

133
Exodus 20:7Deuteronomy 5:11