The most quoted verse in the chapter, and the one most often turned into a return-on-investment promise.
Quick answer
Generosity tends to come back around. The verse reports how life generally runs, which is a very different thing from telling you how to make it run.
Read both lines
The second line supplies the governing image, and it is agricultural rather than financial: he who waters is watered. That is a picture of participation in something circulating, not a transaction with a payout. The word behind "made rich" carries the sense of being made fat or refreshed, which is broader than money and fits the watering image better than a bank balance does. Read with verse 24, the two verses describe a life that stays connected to other people's flourishing and finds, over time, that its own is bound up with theirs.
What it does not mean
This is not a formula for giving in order to get, and it cannot be run as one. Proverbs observes how life generally goes; it does not sign contracts, and the moment generosity is performed to trigger a return it has stopped being the thing the verse is describing. Paul makes the same point in the same agricultural language and then closes the door on the transaction explicitly: give as you purpose in your heart, not grudgingly or of necessity, "for God loves a cheerful giver" (2 Corinthians 9:7). Nor does the verse run backward. A generous person in financial hardship has not failed at this, and no one's giving should ever be measured by their circumstances.
Related: 2 Corinthians 9:6–7 · Proverbs 11:17 · Proverbs 19:17
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.