11 Even a child is known by his doings, whether his work be pure, and whether it be right.
The tree is known by its fruits, a man by his doings, even a young tree by its first fruits, a child by his childish things, whether his work be clean only, appearing good (the word is used Prov. 16:2), or whether it be right, that is, really good. This intimates,
1. That children will discover themselves. One may soon see what their temper is, and which way their inclination leads them, according as their constitution is. Children have not learned the art of dissembling and concealing their bent as grown people have.
2. That parents should observe their children, that they may discover their disposition and genius, and both manage and dispose of them accordingly, drive the nail that will go and draw out that which goes amiss. Wisdom is herein profitable to direct.
– Matthew Henry Commentary