Charles Ellicott 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)

Shall have him become his son at the last.— Confidential slaves sometimes rose to be the heirs of their master’s property. (See above on Proverbs 17:2.) But here the warning seems to be rather against spoiling a slave by over-indulgence, lest he eventually forget his position, just as old and petted servants are apt to become somewhat dictatorial.