One of the sins atoned for by the guilt-offering is robbery. In order for the sacrifice to atone for this sin, however, the robber had to first return the article that he robbed.
Returning Spiritually Robbed Goods
וְהֵשִׁיב אֶת הַגְּזֵלָה אֲשֶׁר גָּזָל וגו': (ויקרא ה:כג)
[G‑d told Moses that if a robber wishes to atone for his sin by offering up a guilt-offering,] he must [first] return the article that he had robbed. Leviticus 5:23

Spiritually, “robbed articles” are anything that we, by sinning, have “robbed” from G‑d and given over to the forces of evil, whether a physical object, a moment in time, or human potential.

Our task in life is to return the world’s robbed entities to their rightful owner, i.e., to reorient everything that has been given over to the cause of evil toward Divinity, beginning with whatever we ourselves have “robbed” from G‑d through our misdeeds. This is the essence of repentance: restoring the world to its natural, Divine state. Through repentance, it is further possible for us to reach even greater heights than we had attained before sinning.1