Heidelberg Catechism – Lord’s Day 43
Q. What is required in the ninth commandment?
A. That I do not bear false witness against anyone, twist anyone’s words, be a gossip or a slanderer, or condemn anyone lightly without a hearing. Rather I am required to avoid, under penalty of God’s wrath, all lying and deceit as the works of the devil himself. In judicial and all other matters I am to love the truth, and to speak and confess it honestly. Indeed, insofar as I am able, I am to defend and promote my neighbor’s good name.