Matthew Poole and continuators on Proverbs 20:11

11 Even a child is known by his doings , whether his work be pure, and whether it be right.

Young Children discover their inclinations or dispositions even by their childish speeches and carriages, as not having yet learnt the art of dissembling.

Or rather, will be; for it is not expressed in the Hebrew, and therefore may be either way supplied. The sense is, The future disposition and conversation of a Man may very probably be conjectured from his childish manners.