Proverbs 16:27

16:27 A wicked scoundrel digs up evil,

and his slander is like a scorching fire.

Proverbs 10:18

10:18 The one who conceals hatred utters lies,

and the one who spreads slander is certainly a fool.

Proverbs 30:10

30:10 Do not slander a servant to his master,

lest he curse you, and you are found guilty.