WSC Q.78: What is forbidden in the ninth commandment?
The ninth commandment forbiddeth whatsoever is prejudicial to truth, or injurious to our own or our neighbour’s good name. (1 Sam. 17:28, Lev. 19:16, Ps. 15:3)
WLC Q.145: What are the sins forbidden in the ninth commandment?
The sins forbidden in the ninth commandment are, all prejudicing the truth, and the good name of our neighbours, as well as our own, (1 Sam. 17:28, 2 Sam. 16:3, 2 Sam. 1:9,10,15–16) especially in public judicature; (Lev. 19:15, Hab. 1:4) giving false evidence, (Prov. 19:5, Prov. 6:16,19) suborning false witnesses, (Acts 6:13) wittingly appearing and pleading for an evil cause, out-facing and overbearing the truth; (Jer. 9:3,5, Acts 24:2,5, Ps. 12:3–4, Ps. 52:1–4) passing unjust sentence, (Prov. 17:15, 1 Kings 21:9–14,10–11,13) calling evil good, and good evil; rewarding the wicked according to the work of the righteous, and the righteous according to the work of the wicked; (Isa. 5:23) forgery, (Ps. 119:69, Luke19:8, Luke 16:5–7) concealing the truth, undue silence in a just cause, (Lev. 5:1, Deut. 13:8, Acts 5:3,8–9, 2 Tim. 4:16) and holding our peace when iniquity calleth for either a reproof from ourselves, (1 Kings1:6, Lev. 19:17) or complaint to others; (Isa. 59:4) speaking the truth unseasonably, (Prov. 29:11) or maliciously to a wrong end, (1 Sam. 22:9–10, Ps. 52:1–5) or perverting it to a wrong meaning, (Ps. 56:5, John 2:19, Matt. 26:60–61) or in doubtful or equivocal expressions, to the prejudice of truth or justice; (Gen. 3:5, Gen. 26:7,9) speaking untruth, (Isa. 59:13) lying, (Lev. 19:11, Col. 3:9) slandering, (Ps. 50:20) backbiting, (James 4:11, Jer. 38:4) talebearing, (Lev. 19:16) whispering, (Rom. 1:29–30) scoffing, (Gen. 21:9, Gal. 4:29) reviling, (1 Cor. 6:10) rash, (Matt. 7:1) harsh, (Acts 28:4) and partial censuring; (Gen. 38:24, Rom. 2:1) misconstructing intentions, words, and actions; (Neh. 6:6–8, Rom. 3:8, Ps. 69:10, 1 Sam. 1:13–15, 2 Sam. 10:3) flattering, (Ps. 12:2–3) vain-glorious boasting; (2 Tim. 3:2) thinking or speaking too highly or too meanly of ourselves or others; (Luke 18:9,11, Rom. 12:16, 1 Cor. 4:6, Acts 12:22, Exod. 4:10–14) denying the gifts and graces of God; (Job 27:5,6, Job 4:6) aggravating smaller faults; (Matt. 7:3–5) hiding, excusing, or extenuating of sins, when called to a free confession; (Prov. 28:13, Prov. 30:20, Gen. 3:12–13, Jer. 2:35, 2 Kings 5:25, Gen. 4:9) unnecessary discovering of infirmities; (Gen. 9:22, Prov. 25:9–10) raising false rumors, (Exod. 23:1) receiving and countenancing evil reports, (Prov. 29:12) and stopping our ears against just defense; (Acts 7:56–57, Job 31:13–14) evil suspicion; (1 Cor. 13:5, 1 Tim. 6:4) envying or grieving at the deserved credit of any, (Numb. 11:29, Matt. 21:15) endeavoring or desiring to impair it, (Ezra 4:12–13) rejoicing in their disgrace and infamy; (Jer. 48:27) scornful contempt, (Ps. 35:15–16,21, Matt. 27:28–29) fond admiration; (Jude 16, Acts 12:22) breach of lawful promises; (Rom. 1:31, 2 Tim. 3:3) neglecting such things as are of good report, (1 Sam. 2:24) and practicing, or not avoiding ourselves, or not hindering what we can in others, such things as procure an ill name. (2 Sam. 13:12–13)