John Gill Commentary Proverbs 29:21

"He that delicately bringeth up his servant from a child Shall have him become a son at the last." — Proverbs 29:21 (ASV)

He that delicately brings up his servant from a child: In a very tender and affluent way uses him with great familiarity; makes him sit at table with him, feeds him with dainties, and clothes him in the most handsome manner, as if he was one of his own children.

[He] will have him become [his] son in the end: He will expect to be used as a son; he will not care to do any servile work, or anything, especially that is hard and laborious; he will be for supplanting the son and heir, and think to inherit all himself; or, however, become proud, haughty, and saucy.

Jarchi interprets this of the evil imagination, or the corruption of nature, which is in a man from a child; which, if cherished and not subdued, will in the end rule over a man: and some apply it to the body; which, if delicately pampered, and not kept under, will be master of the soul, instead of servant to it, and its members be instruments of unrighteousness.