Leviticus 7:29
Speak unto the children of Israel, saying, He that offereth the sacrifice of his peace offerings unto the LORD shall bring his oblation unto the LORD of the sacrifice of his peace offerings. Speak unto the children of Israel, saying, He that offereth the sacrifice of his peace offerings unto the LORD shall bring his oblation unto the LORD of the sacrifice of his peace offerings.
The one who offered the sacrifice of his peace offerings was to bring his oblation to the Lord personally, with his own hands. The peace offering was especially an expression of thanksgiving to God. Only the fat was to be burned upon the altar, while a specified portion including the breast and the right shoulder was reserved for the priests, and the greater remainder was returned to the offerer to be eaten by him and his friends in a sacrificial feast. The burning of the fat pointed forward as a type of the great Sacrifice, the death of Christ to take away the sin of the world, and was designed to preserve faith in the coming Redeemer and to direct all hearts in gratitude and faith to Him.
These directions were violated by priests who were not content with their allotted part, demanding extra meat including the fat that belonged to the Lord without waiting until the fat had been burned, and thereby depriving the offerers of their rightful share. That violation used the great number of sacrifices at the annual feasts to enrich the priests at the expense of the people. They persisted in claiming whatever portion pleased them and threatened to take it by violence if denied.
The requirement to bring with one's own hands teaches personal responsibility and service in which each person has a part to perform that no one else can do by proxy.