Q. 110. What is the third Commandment?
A. Thou shalt not take the Name of the Lord they God in vain, for the Lord will not hold him guiltless that taketh his Name in vain.

Q. 111 What is God’s will for us in the third commandment?
A. That we neither blaspheme nor misuse the name of God by cursing, perjury, or unnecessary oaths, nor share in such horrible sins by being silent bystanders. In a word, it requires that we use the holy name of God only with reverence and awe, so that we may properly confess him,6 pray to him, and praise him in everything we do and say.

Lev. 24:10-17
Lev. 19:12
Matt. 5:37; James 5:12
Lev. 5:1; Prov. 29:24
Ps. 99:1-5; Jer. 4:2
Matt. 10:32-33; Rom. 10:9-10
Ps. 50:14-15; 1 Tim. 2:8
Col. 3:17