We read in Romans 3 of the evil mouth, tongues and throat.
Romans 3:13-14 “Their throats are open graves, their tongues practice deceit.” “The poison of vipers is on their lips.”
You see this is describing an evil mouth. This mouth is an opening where the issues of the heart come forth. This person has an evil heart. The message from the heart is in the mouth.
Romans 10:9-10 If you declare with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. 10 For it is with your heart that you believe and are justified, and it is with your mouth that you profess your faith and are saved.
Under Gods command 