This verse sits inside the second movement of the father's lecture on wisdom and the neighbor, Proverbs 3:21–35.
Quick answer
Do not plot against the neighbor who lives beside you trusting that beside you is a safe place to live. The verse forbids treachery: harm devised against someone whose guard is down because of you.
Read the whole unit
The father's lecture on wisdom and the neighbor moves in three sweeps. First, security (vv. 21–26): keep sound wisdom in view and the results are bodily and immediate, safe steps, unafraid nights, sweet sleep, because "the LORD will be your confidence." Second, the neighbor (vv. 27–31): five consecutive "do nots" that bring wisdom down from the cosmos of the preceding poem to the person next door. Do not withhold good that is owed, do not delay it until tomorrow, do not plot against the neighbor who trusts you, do not pick fights, and do not envy the violent man who seems to be winning. Third, the reasons (vv. 32–35): four verses that ground neighbor-ethics in the LORD's own stances, His abomination and His intimacy, His curse and His blessing, His scorn and His grace, and the divergent inheritances of the wise and the foolish. Some scholars divide the passage at v. 27, treating the neighbor commands as their own unit; the flow of thought holds together as one lecture, since the "do nots" rest directly on the security just described (a person confident in the LORD can afford to be generous and unenvious) and the closing verses supply the reasons for both halves. This entry set treats 3:21–35 as one lecture and notes the boundary question honestly here, once.
What this verse contributes
The aggravating factor is trust. The neighbor has built his life on the assumption that you are not a threat; to devise evil against him is to weaponize nearness, using access that trust granted for harm trust never imagined. The sages rank it accordingly: among the seven things the LORD hates stands "a heart that devises wicked plans" (6:18). The verse's logic extends wherever trust does, the coworker, the partner, the friend with your spare key. Whoever feels safe near you has handed you a small sacred thing.
Related: Proverbs 6:16–19 · Micah 2:1
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.