What does 1 Samuel 2:15 mean?
Eli's sons were priests who served in the temple of the Lord. They have been described as worthless men who did not know the Lord (1 Samuel 2:12). They were deeply involved in open corruption of God's sacrificial laws. The writer has described their custom of taking an extra serving of the meat from those who had come to make sacrifices (1 Samuel 2:13–14).It gets worse. The priests would also send a servant to demand from those bringing sacrifices even more of the meat before it was sacrificed to the Lord or boiled for a meal. In other words, the priests didn't want the meat boiled. They wanted it roasted, and they were willing to violate God's commands for the sacrifice to get it.
The Lord's requirements for the sacrifice were for the fat to be burned first to create an aroma that would please God (Leviticus 3:3–5). The fat was specifically reserved for God. Leviticus 7:25 says, "For every person who eats of the fat of an animal of which a food offering may be made to the LORD shall be cut off from his people." After the fat was burned and the breast was waved as a wave offering, the priests were to be given the breast and the right thigh (Leviticus 7:29–36). Those bringing the sacrifice were to take their portion to be enjoyed as a meal (Leviticus 7:11–18), apparently boiled (Numbers 6:19–20). Eli's sons were demanding meat from those bringing sacrifices before the fat was offered to the Lord and before the meat was boiled so that they could roast it for themselves.