Matthew 5:43-48

43. Ye have heard that it hath been said, Thou shalt love thy neighbor, and hate thine enemy.
44. But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you;
45. That ye may be the children of your Father which is in heaven: For he maketh his sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust.
46. For if ye love them which love you, what reward have ye? do not even the publicans the same?
47. And if ye salute your brethren only, what do ye more than others? do not even the publicans so?
48. Be ye therefore perfect, even as your Father which is in heaven is perfect.

James 3:2-3/8-10

2. For in many things we offend all. If any man offend not in word, the same is a perfect man, and able also to bridle the whole body.
3. Behold, we put bits in the horses' mouths, that they may obey us, and we turn about their whole body.

8. But the tongue can no man tame; it is an unruly evil, full of deadly poison.
9. Therewith bless we God, even the Father; and therewith curse we men, which are made after the similitide of God.
10. Out of the same mouth proceedeth blessing and cursing. My brethren, these things ought not so to be.

Ephesians 4:29

29. Let no corrupt communication proceed out of your mouth, but that which is good to the use of edifying, that it may minister grace unto the hearers.