Psalm 34:13
Keep your tongue from evil and your lips from speaking deceit.
Titus 3:2
To speak evil of no one, to avoid quarreling, to be gentle, and to show perfect courtesy toward all people.
Proverbs 26:20
For lack of wood the fire goes out, and where there is no whisperer, quarreling ceases.
James 4:11
Do not speak evil against one another, brothers. The one who speaks against a brother or judges his brother, speaks evil against the law and judges the law. But if you judge the law, you are not a doer of the law but a judge.
Proverbs 11:13
Whoever goes about slandering reveals secrets, but he who is trustworthy in spirit keeps a thing covered.