Kommentar zu Joel 2:14

Whoever knows—that he is guilty of iniquity.

(14)- and becasue they left Babylonian in the days of Nevuchadnezer therefore it says "who knows if Gd will relent..." who knows the Ways of Gd because there are many ways for Hashem to make things happen and Hashem relented on the bad to allow His nation to return to Jerusalem. Or it means, "who knows the ways of repentence that Hashem relented and returned the blessings to the land in the manner that He returned the Avodah service to the Temple and renewed the mincha offering and libations." And when it says "leave behind a blessing" it is revealed that not all the exiles will return to build the second Temple but only a small portion of the many that were in the original blessing of the land. And when it says "mincha and libation to Hashem" it is revealed that the power of prophecy will not return and neither will the Urim V'tumim or the aron kodesh or the Shechina or the other things except only the korbanot will return like it says "mincha and libation". It's explained in this parsha that the prophet is discussing the destruction of the first Temple and the return from Babylon

shall return and repent, and it shall leave—I.e., the hasil and the gazam will leave a blessing after it; through the repentance, a blessing will come in the produce.