To "despise" a mother is to cause her the deepest grief, and is therefore not unfitly contrasted with "making a glad father."

A wise son maketh a glad father,.... See Gill on Proverbs 10:1;

but a foolish man despiseth his mother; that bore him and brought him up, and perhaps was too indulgent to him; which aggravates his sin and her sorrow; See Gill on Proverbs 10:1; or causes her to be despised by others, as Jarchi interprets it; such a man's sin, which is great folly, and shows him to be a foolish man, is highly resented by the Lord, and will be severely punished; see Proverbs 30:17. The Targum is,

"a foolish son despises his mother;''

and so the Septuagint, Syriac, and Arabic versions, which makes the antithesis more clear; and the Hebrew text designs one grown up to man's estate.

This collection of Solomonic proverbs began, Proverbs 10:1, with a proverb having reference to the observance of the fourth commandment,

(Note: The fifth commandment of the Westminster Shorter Catechism is named as the fourth in Luther's catechism.)

and a second chief section, Proverbs 13:1, began in the same way. Here a proverb of the same kind designates the beginning of a third chief section. That the editor was aware of this is shown by the homogeneity of the proverbs, Proverbs 15:19; Proverbs 12:28, which form the conclusion of the first and second sections. We place together first in this new section, Proverbs 15:20-23, in which (with the exception of Proverbs 15:25) the ישׂמח [maketh glad] of the first (Proverbs 10:1) is continued.

Proverbs 15:20

20 A wise son maketh a glad father,

     And a fool of a man despiseth his mother.

Line first equals Proverbs 10:1. The gen. connection of כּסיל אדם (here and at Proverbs 21:20) is not superlative the most foolish of men, but like פּרא אדם, Genesis 16:12; the latter: a man of the wild ass kind; the former: a man of the fool kind, who is the exemplar of such a sort among men. Piety acting in willing subordination is wisdom, and the contrary exceeding folly.

A wise son maketh a glad father: but a foolish man despiseth his mother.

20. (Compare Pr 10:1).

15:16,17. Believers often have enough when worldly eyes see little; the Lord is with them, without the cares, troubles, and temptations which are with the wealth of the wicked. 18. He that is slow to anger, not only prevents strife, but appeases it, if kindled. 19. Those who have no heart to their work, pretend that they cannot do their work without hardship and danger. And thus many live always in doubt about their state, because always in neglect of some duty. 20. Those who treat an aged mother or a father with contempt or neglect, show their own folly. 21. Such as are truly wise, study that their thoughts, words, and actions should be regular, sincere, and holy. 22. If men will not take time and pains to deliberate, they are not likely to bring any thing to pass. 23. Wisdom is needed to suit our discourse to the occasions. 24. A good man sets his affections on things above; his way leads directly thither.