When was "b'Terem Ledes Chok"?
Rashi: Before the decree came. Radak - i.e. before the Chok of the coming day, i.e. the decree. Malbim - join and gather yourselves beforehand.
Radak citing Targum Yonasan: [Hiskosheshu - fix yourselves] before the decree of Beis Din will come upon you.
What is the comparison to "Motz Avar Yom"?
Rashi: The verse is abbreviated. Like Motz (chaff) that passes in front of wind, and smoke that passes in front of the sun.
Rashi citing Targum Yonasan: Your blood will be like chaff that the wind blows, and like a cloud (some texts - shade) that departs from in front of the day. Radak - Yonason explains that words are omitted.
Radak: The verse should be re-arranged - b'Terem Ledes Chok Yom Motz Avar. I.e. the decree of the day that you will be chaff in front of wind. Many verses must be re-arranged, e.g. "Makom Sham Kever" (Yechezkel 39:11, is like Mekom Kever Sham).
Malbim: This is worse than scattered Kash (straw).
What do we learn from "Lo Yavo Aleichem Yom Af Hashem"?
Malbim: Then, the day of punishments will not come upon you. If you join and gather beforehand, even though the day will come, the anger will not come. Via Teshuvah, even Yom Af Hashem will not come!
