Albert Barnes Commentary Jeremiah 30:7

"Alas! for that day is great, so that none is like it: it is even the time of Jacob`s trouble; but he shall be saved out of it." — Jeremiah 30:7 (ASV)

That day - that is, the day of the capture of Babylon.

It is even the time of Jacob’s trouble - Rather, and it is a time of trouble to Jacob, that is, of anxiety to the Jews, because the customs of war were so brutal that they would be in danger when the enemy made their assault.