Foolishness is bound in the heart of a child. Foolishness (ivveleth) here implies the love of mischief, the waywardness and self-will, belonging to children, bound up in their very nature. Septuagint, "Folly is attached ( ἐξῆπται) to the heart of the young," in which version Cornelius a Lapide sees an allusion to the ornament hung by fond parents round the neck of a child whom they were inclined to spoil rather than to train in self-denying ways.
To such a child folly adheres as closely as the bulla with which he is decorated. But the rod of correction shall drive it far from him. Judicious education overcomes this natural tendency, by punishing it when exhibited, and imparting wisdom and piety (see on Proverbs 13:24 and Proverbs 19:18; and comp.
Proverbs 23:13; Proverbs 29:15; Ecclesiasticus 30:1, etc). The LXX. pursue their notion of the the indulgent parents letting the child have his own way, for they render the last clause, "But the rod and discipline are far from him."