19. Do not speak derogatorily of others

The 19th commandment of Mosaic Law is to not speak derogatorily of others

Where in scripture?

Leviticus  19:16

You shall not go about spreading slander among your kinsmen

New Testament Reference

Titus 3:2

They are to slander no one, to be peaceable, considerate, exercising all graciousness toward everyone.

Code of Canon Law

Can. 220 No one is permitted to harm illegitimately the good reputation which a person possesses nor to injure the right of any person to protect his or her own privacy.

Catechism of the Catholic Church

1853 …The root of sin is in the heart of man, in his free will, according to the teaching of the Lord: "For out of the heart come evil thoughts, murder, adultery, fornication, theft, false witness, slander. These are what defile a man." But in the heart also resides charity, the source of the good and pure works, which sin wounds.

Catholic Encyclopedia

Slander is the attributing to another of a fault of which one knows him to be innocent. It contains a twofold malice, that which grows out of damage unjustly done to our neighbor's good name and that of lying as well. …The important thing to note of slander is that it is a lesion of our neighbor's right to his reputation.

Conclusion

Binding on Christians