Proverbs 13:17 (ESV)

17 A wicked messenger falls into trouble, but a faithful envoy brings healing.

A person who is controlled by a wicked heart will not always speak words that are truthful. The message that he delivers will not be one of good news but rather words of untruth. The consequence of him bringing such a message is that it will be the cause of trouble, both for the receiver of the message and the messenger himself. It will result in the recipient of the message being hurt by gossip, slander and malice. The messenger in turn will be found out for his lies. But a faithful and trustworthy messenger will deliver a message that is truthful. Their message will bring healing such as restoring a broken relationship, correcting a wrong practice and solving a difficult problem.