Eli's sons were wicked men; they had no regard1 for the LORD.
References for 1 Samuel 2:12
Now it was the practice2 of the priests with the people that whenever anyone offered a sacrifice and while the meat3 was being boiled, the servant of the priest would come with a three-pronged fork in his hand.
References for 1 Samuel 2:13
He would plunge it into the pan or kettle or caldron or pot, and the priest would take for himself whatever the fork brought up. This is how they treated all the Israelites who came to Shiloh.
But even before the fat was burned, the servant of the priest would come and say to the man who was sacrificing, "Give the priest some meat to roast; he won't accept boiled meat from you, but only raw."
If the man said to him, "Let the fat4 be burned up first, and then take whatever you want," the servant would then answer, "No, hand it over now; if you don't, I'll take it by force."
References for 1 Samuel 2:16
This sin of the young men was very great in the LORD's sight, for they were treating the LORD's offering with contempt.5
References for 1 Samuel 2:17