WSC Q.77: What is required in the ninth commandment?
The ninth commandment requireth the maintaining and promoting of truth between man and man, (Zech. 8:16) and of our own and our neighbour’s good name, (3 John 12) especially in witness-bearing. (Prov. 14:5,25)
WLC Q.144: What are the duties required in the ninth commandment?
The duties required in the ninth commandment are, the preserving and promoting of truth between man and man, (Zech. 8:16) and the good name of our neighbour, as well as our own; (3 John 12) appearing and standing for the truth; (Prov. 31:8–9) and from the heart, (Ps. 15:2) sincerely, (2 Chron. 19:9) freely, (1 Sam. 19:4–5) clearly, (Josh. 7:19) and fully, (2 Sam. 14:18–20) speaking the truth, and only the truth, in matters of judgment and justice, (Lev. 19:15, Prov. 14:5,25) and in all other things whatsoever; (2 Cor. 1:17–18, Eph. 4:25) a charitable esteem of our neighbours; (Heb. 6:9, 1 Cor. 13:7) loving, desiring, and rejoicing in their good name; (Rom 1:8, 2 John 4, 3 John 3–4) sorrowing for, (2 Cor. 2:4, 2 Cor. 12:21) and covering of their infirmities; (Prov. 17:9, 1 Pet. 4:8) freely acknowledging of their gifts and graces, (1 Cor. 1:4–5,7, 2 Tim. 1:4–5) defending their innocency; (1 Sam. 22:14) a ready receiving of a good report, (1 Cor. 13:6–7) and unwillingness to admit of an evil report, (Ps. 15:3) concerning them; discouraging tale-bearers, (Prov. 25:23) flatterers, (Prov. 26:24–25) and slanderers; (Ps. 101:5) love and care of our own good name, and defending it when need requireth; (Prov. 22:1, John 8:49) keeping of lawful promises; (Ps. 15:4) studying and practicing of whatsoever things are true, honest, lovely, and of good report. (Phil. 4:8)