Commentaire sur Le Lévitique 5:23

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).

והשיב את הגזלה..ואת אשמו יביא, the sacrifice does not achieve atonement until the guilty party has first satisfied the demands on him by the injured party.

והיה כי יחטא ואשם, “it will be when he has sinned and realises his guilt, etc.” The reason why the Torah repeats the words meaning “he has sinned,” using both the term יחטא and אשם is to bring home the point that in all these instances the sin is two-fold. The sinner committed a crime against his fellow man but he also sinned against G’d the Law giver. The sin discussed in this verse is an intentional one. This is why the paragraph commences with the words נפש כי תחטא instead of writing merely כי תחטא בשגגה, “if he sinned erroneously.” All the other instances in which the Torah has used the term חטא the word בשגגה, “inadvertently,” or words to that effect accompanied the term חטא (compare 4,2; 4,22; 4,27; 5,15). It is a well known fact that most sin-offerings are brought only in respect of unintentionally committed sins. There are only four instances when a guilt-offering is prescribed for sins committed knowingly; they are: 1) if someone slept with a Gentile servant girl (slave); 2) a Nazirite who defiled himself; 3) swearing a false oath as part of one’s testimony. 4) swearing a false oath concerning matters entrusted to him (compare Keritut 9).