Deuteronomy 5:20

m You shall not bear dishonest witness against your neighbor. 

m. [5:20] Dt 19:15–19; Ex 20:16; 23:1–3; Lv 19:11, 15–16; 1 Kgs 21:1–19; Ps 5:6–10; 10:7–9; 27:12; Prv 25:18; 30:8–10; Jer 7:9; Hos 4:2; Mt 19:18; 26:59–60; Mk 10:19; Lk 18:20. 

people who don't tell the truth can create all kinds of trouble. 

attribution: BLINDFOLD