Heidelberg Catechism – Lord’s Day 36
Q. What is required in the third commandment?
A. That we must not profane or abuse the name of God by cursing, by perjury, or by unnecessary oaths. Nor are we to participate in such horrible sins by keeping quiet and thus giving silent consent. In a word, we must not use the holy name of God except with fear and reverence so that he may be rightly confessed and addressed by us, and be glorified in all our words and works.
Q. Is it, therefore, so great a sin to blaspheme God’s name by cursing and swearing that God is also angry with those who do not try to prevent and forbid it as much as they can?
A. Yes, indeed; for no sin is greater or provokes his wrath more than the profaning of his name. That is why he commanded it to be punished with death.