Heidelberg Catechism, Lord’s Day 36
Q99. What is required
in the third commandment?
A99. We are not to blaspheme or to abuse the name of God
or unnecessary oaths,
nor to share in such horrible sins
by being silent bystanders.
Rather, we must use the holy name of God
only with fear and reverence,
so that we may rightly confess him,
call upon him,
and praise him in all our words and works.
Q100. Is the blaspheming of God’s name
by swearing and cursing
such a grievous sin
that God is angry also with those
who do not prevent and forbid it
as much as they can?
for no sin is greater
or provokes God’s wrath more
than the blaspheming of his name.
That is why he commanded it to be punished