The 9th commandment restricts “bearing false witness against your neighbor.” We usually interpret this to mean “do not lie.” See Exodus 20:16; Eph. 4:25, 29; James 3:5-10.
New Revised Standard Version
16 You shall not bear false witness against your neighbor.
James 3:1-10 (NRSV)
Not many of you should become teachers, my brothers and sisters, for you know that we who teach will be judged with greater strictness. 2 For all of us make many mistakes. Anyone who makes no mistakes in speaking is perfect, able to keep the whole body in check with a bridle. 3 If we put bits into the mouths of horses to make them obey us, we guide their whole bodies. 4 Or look at ships: though they are so large that it takes strong winds to drive them, yet they are guided by a very small rudder wherever the will of the pilot directs. 5 So also the tongue is a small member, yet it boasts of great exploits.
How great a forest is set ablaze by a small fire! 6 And the tongue is a fire. The tongue is placed among our members as a world of iniquity; it stains the whole body, sets on fire the cycle of nature, and is itself set on fire by hell. 7 For every species of beast and bird, of reptile and sea creature, can be tamed and has been tamed by the human species, 8 but no one can tame the tongue—a restless evil, full of deadly poison. 9 With it we bless the Lord and Father, and with it we curse those who are made in the likeness of God. 10 From the same mouth come blessing and cursing. My brothers and sisters, this ought not to be so.
Eph. 4:25-29 (NRSV)
25 So then, putting away falsehood, let all of us speak the truth to our neighbors, for we are members of one another. 26 Be angry but do not sin; do not let the sun go down on your anger, 27 and do not make room for the devil. 28 Thieves must give up stealing; rather let them labor and work honestly with their own hands, so as to have something to share with the needy. 29 Let no evil talk come out of your mouths, but only what is useful for building up, as there is need, so that your words may give grace to those who hear.