Leviticus 7:32
And the right shoulder shall ye give unto the priest for an heave offering of the sacrifices of your peace offerings. And the right shoulder shall ye give unto the priest for an heave offering of the sacrifices of your peace offerings.
The peace offering was especially an expression of thanksgiving to God, designed to preserve faith in the coming Redeemer by pointing forward to the death of Christ, so that all hearts would be directed in gratitude and faith to the great Sacrifice that would take away the sin of the world. In this law the fat alone was to be burned upon the altar, for it belonged to God and was not to be eaten. A specified portion, including the right shoulder as a heave offering, was reserved for the priests as their allotted share.
The greater part, the rest of the offering, was returned to the one who brought it to be eaten by him and his friends in a sacrificial feast. These directions were precise, keeping each portion clear. Eli's sons served as priests though wholly unfit for the priesthood, and they disregarded the law of the offerings.
Hophni and Phinehas violated this order by demanding the meat before the fat had been burned to God and refusing to wait for that burning. Not content with the allotted portion, they demanded an additional portion and persisted in claiming whatever portion pleased them. Using the great number of sacrifices at the annual feasts to enrich themselves at the people's expense, they took more than their rightful share and threatened to take it by violence when denied, even by force.