The Heidelberg Catechism: Lord’s Day 43

112. Question: What is required in the ninth commandment?

Answer: I must not give false testimony against anyone, twist no one’s words,  not gossip or slander, nor condemn or join in condemning anyone rashly and  unheard.[1] Rather, I must avoid all lying and deceit as the devil’s own works, under penalty of God’s heavy wrath.[2] In court and everywhere else, I must love the truth,[3] speak and confess it honestly, and do what I can to defend and promote my neighbor’s honor and reputation.[4]

 [1] Ps. 15; Prov. 19:5, 9; 21:28; Matt. 7:1; Luke 6:37; Rom. 1:28-32. [2] Lev. 19:11, 12; Prov. 12:22; 13:5; John 8:44; Rev. 21:8. [3] I Cor. 13:6; Eph. 4:25. [4] I Pet. 3:8, 9; 4:8.