Israel"s election as a nation did not preclude God"s judgment of the unbelievers in it. His mercy and faithfulness are observable in His sparing a remnant. Isaiah 10:22-23 anticipated the depletion of Israel through Sennacherib"s invasion. That was God"s instrument of judgment. When Paul wrote, the believing remnant of Israel was within the church, as it is today. [source][source][source]