What does Proverbs 5:16 mean?

Here Solomon stresses the folly of adulterous relationships. Scholars are split on whether the phrasing in this verse is meant as a reference to a person's passions, or to children, or possibly both.

The prior verse compared enjoying a faithful marriage to drinking water from a person's own well or cistern. That comes with many advantages, including knowing for sure that the water is pure and safe. It also implies a sense of legitimacy—a satisfaction of knowing that the water is coming from an appropriate source. This verse seems to contrast that to someone who drinks water from random locations, or even out of trickles running through the dirt of a street. Those would be less-appealing and dangerous ways to satisfy thirst.

Also, concepts like wells and cisterns imply control: the water is being cared for and managed in the right way. Sexuality is much the same—it needs to be carefully managed, not carelessly thrown around. The imagery of wasting water in the streets is a contrast to that idea, as well.

Alternatively, there is the fact that human sexuality is connected to bearing children. One possibility of adulterous relationships is the births of unexpected children. In the ancient world, as in the modern day, so-called "unwanted" children face many challenges. Those not heartlessly killed in abortion may be destined to live in less-than-ideal conditions, or even abandoned as orphans. God's order for society is the family unit: children in the care of one man and one woman.

Of course, in some cases, a couple may be childless, but God always does what is right and best. A husband never has a reason to be unfaithful to his wife. Childless Abraham and Sarah decided not to wait for Isaac whom God promised would be born to them in their old age. At Sarah's suggestion, Abraham had relations with her servant Hagar. Abraham followed Sarah's suggestion, and as a result Ishmael was born (Genesis 16:1–4). God predicted Ishmael would be a source of conflict, and the prediction came true. Even today, the descendants of Ishmael oppose the descendants of Isaac (Genesis 16:12).