This verse closes the king run, Proverbs 16:10–15.
Quick answer
The king's smile is life-giving weather: his shining face means safety, and his favor is the spring rain that fattens the harvest. When the most powerful face in the room is for you, everything grows.
Read both lines
This is the photographic negative of v. 14: there the king's wrath was messengers of death, here the light of his face is life, language reaching back to the blessing every Israelite knew, "the LORD make His face shine upon you" (Numbers 6:25). The latter rain came just before harvest and decided its size; favor from the throne arrived like that. The run closes with the reader trained to want a king like this, and Scripture's long answer is that the face this verse describes belongs finally to God.
From this side of the cross
The gospel's boldest claim about the believer is where he now stands: in the light of the King's face, permanently, "the light of the knowledge of the glory of God in the face of Jesus Christ" (2 Corinthians 4:6). The favor is not seasonal weather anymore. It is the climate.
Related: Numbers 6:24–26 · Psalm 30:5 · 2 Corinthians 4:6
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.