Parsha Mitzvot: Vayikra: Mitzvah 124 – Concept 433
“So it shall be that when he will sin and become guilty, he shall return the robbed item that he robbed, or the proceeds of his fraud, or the pledge that was left with him, or the lost item that he found; or anything about which he has sworn falsely – he shall repay its principal and add its fifth to it; he shall give it to its owner on the day he admits his guilt. And he shall bring his guilt-offering to God, an unblemished ram from the flock, of the proper value, as a guilt-offering, to the Kohen.” (Leviticus 5:23-25) A person shall bring an Asham Vidai when (certain) guilt is ascertained. (Rambam, Hilchot Shegagot – The Laws of Offerings for Unintentional Transgressions)
Only after requiring him to return the stolen goods does the Torah say that he must bring his guilt-offering. God does not forgive a sinner until he first appeases the victim of his misdeed.