Proverbs 25:18 (AMP): A man who bears false witness against his neighbor is like a heavy sledgehammer and a sword and a sharp arrow.
This verse from Proverbs describes how a person who is a false witness affects another — it is like a sharp and heavy blow against them. God commanded us not to bear false witness against anyone, and it is the ninth commandment in the list of the Ten Commandments in the Old Testament.
Exodus 20:16: Thou shalt not bear false witness against thy neighbour.
The definition of a “false witness” is someone who lies about his neighbor or anyone else. Bearing false witness is telling a lie or witnessing with a false report. But this commandment has a deeper meaning than just lying. The Bible makes some very strong statements about how we speak and how we “witness” with our mouths – both positive and negative. Now, bearing false witness would include gossiping, slander, lying, deceitfulness and cheating. When we gossip about anybody, we are lying about them and bearing false witness about them. This is a very serious thing before God. According to this verse in Proverbs, it is like beating someone with a heavy sledgehammer or hitting them with a sword or an arrow.