This verse sits inside Folly's banquet, Proverbs 9:13–18, and is Wisdom's own invitation repeated word for word.
Quick answer
The same sentence Wisdom spoke in verse 4, aimed at the same two people. The chapter deliberately gives both women the identical line.
Read the whole unit
The chapter's second table, and the second woman. Everything about her is arranged to mirror the first, and the mirroring is the argument.
Wisdom built a house; this woman already has one and sits at its door. Wisdom hewed pillars, slaughtered, mixed, and set a table; this woman prepares nothing at all. Wisdom sent servants out into the city; this woman sits on a seat. Wisdom called from the highest places of the city; so does she, from the same phrase. And her invitation in verse 16 is, in Hebrew, word for word the same sentence Wisdom spoke in verse 4, addressed to the same two people, the simple and the one lacking heart.
Then the two offers diverge, and the difference is not what anyone would predict. Wisdom offered bread and wine she had made. This woman offers water and bread that are stolen and eaten in secret. Same two categories, and the entire appeal has moved from the food to its provenance. Nothing is claimed about the taste except that being illicit is what makes it sweet.
Two things must be said about how these verses are read.
Verse 17 is a character speaking, and the catalog flags it every time. "Stolen water is sweet, and bread eaten in secret is pleasant" is not the book's counsel and not an endorsement. It is Folly's sales line, quoted so the reader can hear it, and verse 18 immediately supplies the narrator's correction. Lifted out of the chapter, it has been quoted as though Proverbs were observing something wistful about forbidden pleasure. Proverbs is doing the opposite: it is showing you the pitch, and then showing you the guest list.
This is not a chapter about women, and its own design forecloses that. Two women are set against each other here, and the one the book wants you to follow is a woman. The figure who builds, provides, sends, and gives is female, and so is the figure who takes. Anyone reading chapters 5 through 9 as a warning about women has to explain why this book's own embodiment of the good life keeps a house and sets a table. Both figures are personifications, and the contest is between two ways of living, not between a man and a danger.
What this verse contributes
This verse is the hinge the whole chapter turns on, and its content is a quotation. In Hebrew it repeats verse 4 exactly apart from two small connecting words, addressing the simple and the one lacking heart, and issuing the same invitation to turn in. The book could have made Folly's pitch obviously worse and chose not to. What it teaches by the repetition is that discernment cannot run on the sound of an invitation, because the two most opposed voices in Collection I use the same words in the same place to the same people. The difference is entirely in what happens after the door.
Related: Proverbs 9:4 · Proverbs 9:18 · Proverbs 14:12
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.