1 Samuel 2

"Now it was the practiceof the priests that, whenever any of the people offered a sacrifice, the priest’s servant would come with a three-pronged fork in his hand while the meat was being boiled 14 and would plunge the fork into the pan or kettle or caldron or pot. Whatever the fork brought up the priest would take for himself. This is how they treated all the Israelites who came to Shiloh. 15 But even before the fat was burned, the priest’s servant would come and say to the person who was sacrificing, “Give the priest some meat to roast; he won’t accept boiled meat from you, but only raw.”

16 If the person said to him, “Let the fat be burned first, and then take whatever you want,” the servant would answer, “No, hand it over now; if you don’t, I’ll take it by force.” vv.14-16

Read chapter 2

Eli's sons were corrupt priests. In the law there were specific instructions of offerings that were for the Lord and portions that were for the priests yet Hophni and Phinehas extorted the law and even shows that the people knew better of what was for the priests and what was for the Lord only.  We read of these specific laws in Leviticus:

"Anyone who eats the fat of an animal from which a food offering may be[c] presented to the Lord must be cut off from their people." Lev. 7:25.

"The priest shall burn the fat on the altar, but the breast belongs to Aaron and his sons. 32 You are to give the right thigh of your fellowship offerings to the priest as a contribution. 33 The son of Aaron who offers the blood and the fat of the fellowship offering shall have the right thigh as his share. 34 From the fellowship offerings of the Israelites, I have taken the breast that is waved and the thigh that is presented and have given them to Aaron the priest and his sons as their perpetual share from the Israelites.’”  This is the portion of the food offerings presented to the Lord that were allotted to Aaron and his sons on the day they were presented to serve the Lord as priests." Lev. 7:31-35

This corruption of Hophni and Phinehas led the people to abhorred the offering of the Lord.  Oh how sad when wicked leaders cause others to sin and go astray.  Also to see that Eli their father knew of their sin but didn't seem to discipline till it was too late.