Quick answer
A murderer running for his life is described, and the verse says not to stop his fall. It is one of the hardest sentences in the book.
Read both lines
The first line is a picture of flight without refuge. The man is עָשֻׁק בְּדַם־נָפֶשׁ, oppressed or burdened with the blood of a life, and he runs toward a pit, which in this book is where the trap-setter ends up. Nothing suggests he is being pursued by anyone but the thing he did.
The second line is the difficulty. It is a command, and it forbids intervention. In the covenant's own legal framework a deliberate killer had no city of refuge available to him and no ransom could be accepted for his life, so the saying is not inventing cruelty; it is refusing to obstruct a judicial reckoning the community had already agreed to.
What it does not mean
This is not a verse about withholding help from people in trouble, and it must never be generalized. Its subject is one specific person, a man with blood on him, inside an ancient legal system that had decided how such cases were handled. It says nothing about the poor, the addicted, the imprisoned, the guilty of lesser things, or anyone whose situation is uncomfortable to be near. The book's own instinct runs hard the other way, commanding rescue for those being carried toward death at 24:11 and generosity to the poor eight verses later at 28:27. Anyone using 28:17 to justify turning away from a person in need has taken a narrow judicial saying and made it a disposition.
Related: Proverbs 24:11–12 · Proverbs 28:27 · Numbers 35:31 · Proverbs 26:27
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.