The 73rd mitzvah is that we are commanded to verbally acknowledge the sins we have committed before G‑d (exalted be He), when we come to do teshuvah (to repent). This is vidui (verbal confession), the idea of which is to say, "O G‑d, I have sinned, I have committed iniquity, I have transgressed and done ..." One should elaborate verbally and ask for atonement on this transgression with all the eloquence at his command.
You must understand that even for those sins which require one to bring certain sacrifices, as described above, (and regarding which G‑d (exalted be He) has said that the one who offers them thereby receives atonement) one must recite vidui at the time of the sacrifice.
The source of this commandment is G‑d's statement (exalted be He), "Speak to the Israelites: A man or woman who does any sin against his fellow man, ... must recite vidui on their sins that they have committed."
The Mechilta explains the meaning of this verse: "Since it is written, 'he must recite vidui [on it] for the sin that he has committed,' we learn that one must recite vidui for a sin. Since the verse adds '[he must recite vidui] on it,' we learn that the vidui must be said when the animal is still alive, rather than after it has been slaughtered. However, from this we may derive the necessity of reciting vidui only for the transgression of an impure person entering the Temple."
G‑d's statement (exalted be He), "[he must recite vidui] on it for the sin that he has committed," — is written in parshas Vayikra regarding an impure person entering the Temple or eating sanctified food, and the other related cases we mentioned previously. Therefore, the Mechilta says that the only obligation of vidui to be derived from this verse is for an impure person who has entered the Temple [or the related cases].
"How do we derive [the obligation of vidui] for all other mitzvos? From the verse, 'Speak to the Israelites: ... they must recite vidui...' How do we know that even those punishable by death and by kares must recite vidui? From the expression, 'their sins.' The expression, 'any of their sins,' comes to include [the necessity of vidui] for any prohibition. The expression, 'who does,' comes to include the positive mitzvos."
There it continues [to interpret this verse]: "'Any sin against his fellow man,' comes to include any interpersonal transgression, such as theft, robbery, or lashon hara. The expression, 'Being untrue [to G‑d],' comes to include one who swore falsely using G‑d's Name, and one who curses Him. The expression, 'Becomes guilty of a crime,' comes to include those who are punishable by death — that all the above are obligated to recite vidui. One might think that one who is executed due to false testimony [must also recite vidui] — however, the verse only says, 'And he becomes guilty of a crime.' " This means that the individual must recite vidui only if he knows that he sinned, not if he was convicted by false testimony.
It has therefore been explained to you that one must recite vidui for all categories of sin — more severe and less severe, and even positive mitzvos.
However, since this commandment, "They must recite vidui," is mentioned together with the obligation to bring the appropriate sacrifice, one might think that vidui is secondary to the sacrifice, rather than a distinct mitzvah on its own. Therefore the Mechilta must continue:
"One might think that the obligation to recite vidui applies only when bringing a sacrifice. How do we know that it applies even when no sacrifice is brought? This we learn from the statement, 'Speak to the Israelites ... they must recite vidui.' We still only know of the obligation of vidui in Israel. How do we know it applies even in exile? This we learn from what Daniel said, 'They will then recite vidui for their sins and the sins of their fathers,' and from the verse, 'To You, G‑d, there is charity, and to us there is shame.' "
From all of this it is understood that vidui is a distinct mitzvah for itself; and that it is obligatory for anyone who commits any type of sin, whether in Israel or outside of Israel, whether or not accompanied by a sacrifice. [In all cases,] he is required to recite vidui, G‑d (exalted be He) stated, "They must recite vidui for their sins that they have committed."
The Sifri also explains the verse in this way: " 'And he must recite vidui' — this refers to verbal confession."
The details of this mitzvah have been explained in the last chapter of tractate Kippurim [Yoma].
