וְהָיָה֮ כִּֽי־יֶחֱטָ֣א וְאָשֵׁם֒ וְהֵשִׁ֨יב אֶת־הַגְּזֵלָ֜ה אֲשֶׁ֣ר גָּזָ֗ל א֤וֹ אֶת־הָעֹ֙שֶׁק֙ אֲשֶׁ֣ר עָשָׁ֔ק א֚וֹ אֶת־הַפִּקָּד֔וֹן אֲשֶׁ֥ר הָפְקַ֖ד אִתּ֑וֹ א֥וֹ אֶת־הָאֲבֵדָ֖ה אֲשֶׁ֥ר מָצָֽא׃
Tze'enah Ure'enah
“Restore that which he got through robbery or fraud” [5:23]. Bahya asks a question. Why did it have to say, “that he stole,” that he should return the robbery that he had stolen, but it says he should return that which he stole? The explanation is that this teaches us that he must return what he stole. However, if he wants to return money, he should not do this. The Talmud says in [tractate] Baba Kama. If a person has stolen a beam and had built it into his house, he is obligated to tear down the whole house and take out the beam in order to return it. However, he cannot pay money for the beam; that does not help. However, the House of Hillel says that they made a regulation that one should accept money for the beam, expecting that the person would quickly repent. He should not say, I will gladly return the beam, but it is difficult to tear down the whole house. Therefore, one should accept money for the beam. It is known that there are two types of sins. One is that the person commits sins against the Holy One; he does this to his own soul. The other one are the sins that he does to his friend. He denigrates or assaults him. He only sins against a person. However, the one who steals, also sins against God. Therefore, the sin is more severe than all the other sins in the world. The Flood was caused for no other reason than stealing. Ezekiel had punished Israel for their sins. He said: you have spilled blood and have shamed My holiness, and have engaged in slander and taken usury. You have forgotten Me and at the very end says, you have stolen. Therefore, I want to kill you. Here it is heard that God kills and punishes the person because of stealing.24Bahya, Leviticus, 5:23.
Rashi
יחטא ואשם כי means when he comes to a recognition of himself (recognises his duty) to repent of his sin and makes up his mind to confess that he has sinned and has incurred guilt).
Kli Yakar
And it shall be when he sins and acknowledges his guilt. Rashi explains: When he recognizes within himself to return in repentance, etc. For every sinner never places blame on himself, and a man’s way is right in his own eyes because he justifies himself in all his ways, saying that this person owes him from elsewhere according to his imagination, or it seems to him that he has done him some injustice, therefore he withholds his deposit. Consequently, on the day that he places guilt upon himself and recognizes his error, and that he has not done good among his people, this is what it means by and acknowledges his guilt — that he blames himself, and he too instructs himself about the prohibition by recognizing his sins, and then he will certainly take to heart to return in repentance. And he shall return the stolen item that he stole — not that he should pay the value of the stolen item, but rather the actual item that he stole. And he shall pay it in its principal, etc. — For the Holy One, blessed be He, gives up what is His and does not insist if one delays bringing his guilt offering to God. Therefore, He commanded him to prioritize payment to the person, to give him first all that is his, and afterward he shall bring his guilt offering for the oath, and he shall add its fifth part to it — because his money was idle with him.