How will the nation of Israel come to believe in Jesus?
The nation of Israel will come to believe in Jesus when they see their resurrected Lord and Messiah King coming in the clouds of glory at His Second Coming, at the end of the Tribulation. A remnant will be saved in a moment, experiencing resurrection power.
Les explains that God's timetable places the birth of the nation of Israel at the end of the Tribulation, at the Second Coming of Christ. Paul was saved 2,000 years earlier, like a preemie delivered prematurely. Just as Paul was miraculously saved on the road to Damascus, so also the nation of Israel will yet be saved—not all, but the remnant. They will experience the same kind of resurrection power, see their resurrected Lord and Messiah and King coming in the clouds of glory, and then believe in a moment. That is what Paul means by being born before the due time.