Albert Barnes Commentary 1 Kings 12:10

"And the young men that were grown up with him spake unto him, saying, Thus shalt thou say unto this people that spake unto thee, saying, Thy father made our yoke heavy, but make thou it lighter unto us; thus shalt thou speak unto them, My little finger is thicker than my father`s loins." — 1 Kings 12:10 (ASV)

My little finger ... - that is, “You shall find my hand heavier on you than my father’s—as much heavier as if my little finger were thicker than his loins.”