Foolishness [is] bound in the heart of a child
That is, sin, the greatest of all folly; this is naturally in the heart of man; it is in the heart of a child, it is in him from his infancy; it is bound in his heart, it is rooted and riveted in him, being conceived in sin, and shapen in iniquity; it is what cleaves close to him, and he has a strong affection for and desire after: the imagination of man's heart is evil from his youth, ( Genesis 8:21 ) ; so that he is not easily brought off of sin, or becomes wise; [but] the rod of correction shall drive it far from him;
the rod used by parents, for the correction of sin and folly, is a means of making children wise, and of restraining the folly that is bound up in them; and of reclaiming them from those sinful ways, which the folly of their hearts leads them to, and so in some measure of driving it far from them.