Proverbs 5:18 - Joseph Benson’s Commentary on the Old and New Testaments

Let thy fountain be blessed Thy wife, as the next clause explains it, shall be blessed with children; or rather, she shall be a blessing and a comfort to thee, as it follows, and not a curse and snare, as a harlot would be. And rejoice, &c. Seek not to harlots for that comfort and delight which God allows thee to take in thy wife. So here he explains the foregoing metaphor, and applies it to its present design; with the wife of thy youth Whom thou didst marry in thy youthful days, with whom, therefore, in all reason and justice, thou oughtest still to satisfy thyself, even when she is old.