1 Samuel 2:13-14

13The custom of the priests with the people was that when any man offered sacrifice, the priest's servant would come, while the meat was boiling, with a three-pronged fork in his hand,

14and he would thrust it into the pan or kettle or cauldron or pot. All that the fork brought up the priest would take for himself. This is what they did at Shiloh to all the Israelites who came there.