THUMB.The thumb is associated with the great toe, and occurs in two different connexions. 1. We are told that Adonibezeks thumbs and great toes were cut off (Jdg_1:8), and that he himself had practised this mutilation on seventy kings (Jdg_1:7). The object seems to have been to render the vanquished monarchs unfit for war and thus for reigning in a warlike age. 2. In the ritual of the consecration of Aaron and his sons (Exo_29:20, Lev_8:23-24) blood was sprinkled on the tip of the right ear, upon the thumb of the right hand and the great toe of the right foot. The cleansed leper was similarly sprinkled with blood and oil (Lev_14:14; Lev_14:17; Lev_14:25; Lev_14:28). The action seems to have symbolized the consecration (or purification) of the whole man, the extremities only being touched, just as only the horns of the altar were sprinkled with the blood.
W. F. Boyd.
Hastings' Dictionary of the Bible
Edited by James Hastings, D.D. Published in 1909
Lev_14:14 (b) This type is used to represent the work and works of the priest. The blood and the oil on the thumb indicate that all the service of the servant of GOD was henceforth to be dedicated only to GOD. JESUS' whole hands were covered with blood, for He worked only for the Father. (See also Lev_8:23; Exo_29:20).
Wilson's Dictionary of Bible Types
press 1957.