Sforno on Deuteronomy 30:11/ספורנו על דברים ל׳:י״א

1כי המצוה הזאת, and the reason that I said in verse 1 that the repentance must be wholehearted and among the nations, i.e. while you are still in exile, is so that it can trigger your salvation. For, indeed this commandment, i.e. the one to return to G’d in sincere penitence אשר אנכי מצוך היום, Moses reminds the people that in the list of sacrifices in Leviticus 5,5 et al, where various kinds of sin and guilt offerings are listed as means to expiate for the error committed, the essential refrain is always “והתוודה אשר חטא,” that the guilty person first confesses his mistake, his sin, even the one committed inadvertently. Compare also Numbers 5,6-7)

2לא נפלאת היא ממך, so that you would need to ask the prophets in order to understand it correctly.

3ולא רחוקה היא, so that you have to ask the leading Torah scholars of your generation who live a long way from you to explain how to observe this commandment. You can easily observe this commandment even in the Diaspora where you may not have any Torah scholars nearby.