You can take a drop from a bottle of vinegar, put it on the tip of your tongue, and tell what is in the rest of the bottle. You don’t need to drink the whole thing to make sure. And this relates to a basic question in pastoral counseling. “What’s your mouth like?”
And Jesus said that “out of the abundance of the heart the mouth speaketh” (Matt. 12:34). That means if your mouth is an open sewage pipe dumping into the clean river of God’s creation, your heart is the sewage lagoon. And if your heart is a sewage lagoon, the first order of business is getting a new heart. That means the new birth.
What is one description of unregenerate man? “Whose mouth is full of cursing and bitterness” (Rom. 3:14).
What kind of mouth has no inheritance in the kingdom of Christ and God (Eph. 5:5)? This kind—“neither filthiness, nor foolish talking, nor coarse jesting, which are not fitting, but rather giving of thanks” (Eph. 5:4, NKJV).
What is the new man told to be like, in contrast to the old mouth? “Let no corrupt communication proceed out of your mouth, but that which is good to the use of edifying, that it may minister grace unto the hearers” (Eph. 4:29).
Of course we are talking about actual humans, and not a row of cinder blocks. This means that we have to understand the real nature of language, the possibility of backsliding, the relationship of justification and sanctification, and more. But with all due qualifications made, we still have to acknowledge the basic spiritual reality here. People with a foul mouth need to get saved.