Leviticus 23:19

Then ye shall sacrifice one kid of the goats for a sin-offering, and two lambs of the first year for a sacrifice of peace-offerings. "The sin-offering was to excite the feeling and consciousness of sin on the part of the congregation of Israel, that, whilst eating their daily leavened bread, they might not serve the leaven of their old nature, but seek and implore from the Lord, their God, the forgiveness and cleansing away of their sin. " (Keil.)