Below are some important thoughts from Reggie Kelly on Matthew 23:39. He rightly challenges the overly optimistic view of the prophecy that has been popularized in recent decades in the establishment of the State of Israel.
There can be no doubt that throughout the tribulation, there will be a burgeoning remnant of Jews that will be born again, no doubt much greater than usual. But this is not the “mercy upon all” that was spoken by the prophets and reaffirmed by Paul in Ro 11:26, 32. This does not happen till the Deliverer comes out of Zion at the day of the Lord.