C. F. Keil and Franz Delitzsch on Proverbs 29:15

Pro 29:15

A proverb with שׁבט, Pro 29:15, is placed next to one with שׁופט, but it begins a group of proverbs regarding discipline in the house and among the people: 15 The rod and reproof give wisdom;      But an undisciplined son is a shame to his mother.

With שׁבט [a rod], which Pro 22:15 also commends as salutary, תּוכחת refers to discipline by means of words, which must accompany bodily discipline, and without them is also necessary; the construction of the first line follows in number and gender the scheme Pro 27:9, Zec 7:7; Ewald, §339c. In the second line the mother is named, whose tender love often degenerates into a fond indulgence; such a darling, such a mother’s son, becomes a disgrace to his mother. Our “ausgelassen,” by which Hitzig translates משׁלּח, is used of joyfulness unbridled and without self-restraint, and is in the passage before us too feeble a word; שׁלּח is used of animals pasturing at liberty, wandering in freedom (Job 39:5; Isa 16:2); נער משׁלח is accordingly a child who is kept in by no restraint and no punishment, one left to himself, and thus undisciplined (Luther, Gesenius, Fleischer, and others).