This verse sits inside the father's lecture on guarding the heart, Proverbs 4:20–27, the first of the downstream verses that follow the guarded heart.
Quick answer
The first outlet downstream of the heart is the mouth: put crooked speech away from you, and put it far.
Read the whole unit
The father's lecture on guarding the heart is a body in order. It begins at the ear (v. 20): give attention, incline the ear to a father's words. It moves to the eyes and the heart (v. 21): keep the words in sight and store them at the center. It pauses to state what the words are worth (v. 22): life to those who find them, health to all their flesh. Then it arrives at the summit of the chapter and one of the summits of the book (v. 23): keep your heart with all diligence, for out of it spring the issues of life. In Hebrew thought the heart is not the seat of sentiment but the control room of the whole person, where thinking, desiring, and deciding live, and the verse names it a wellspring: everything a life produces flows up from there. What follows is not a new subject but the same subject walking: the mouth (v. 24), deceit and perversity put far away; the eyes (v. 25), fixed straight ahead; the feet (vv. 26–27), their path pondered, their steps established, swerving neither right nor left. The order is the teaching. The lecture does not begin with behavior and hope it seeps inward; it begins at the center and works outward, because mouth, eyes, and feet are downstream organs. They carry whatever the spring sends them.
What this verse contributes
This verse begins the lecture's tour of the outlets, and it starts with the mouth because the mouth is the heart's nearest exit. "Deceitful" carries the NKJV's footnote "devious": speech bent from true, and the twin commands are distance commands, put it away, put it far, the same geography the lecture used for the wicked path. Standing where it stands, the verse makes a diagnostic point as much as a moral one: crooked talk in the outflow means something upstream needs attention, for the mouth speaks from the heart's abundance. But the father still addresses the mouth directly, because outlets can be tended while the spring is being kept.
Related: Proverbs 6:12 · Ephesians 4:29
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.