Deuteronomy 19:18 And the judges shall make diligent inquisition: and, behold, if the witness be a false witness, and hath testified falsely against his brother; 19 Then shall ye do unto him, as he had thought to have done unto his brother: so shalt thou put the evil away from among you.
People like to gossip and spread lies about others. God had a plan in place in Israel that would stop that. He said that when accusations were made that they were to diligently investigate.
If they found out that someone was lying then whatever the liar was trying to cause to happen to the accused was to be applied to that person.
This was the way to stop the evil among the people of Israel. So be careful not to lie about your brother in Christ or anyone else for that matter.
The evil you desire to see happen to the other would be applied to you! So be careful not to lie about others.