What did Israel's rejection of God's promises actually accomplish for salvation?
Israel’s rejection of everything God had promised brought about what had to be done for salvation: His sacrificial death, burial, and resurrection. Their unbelief did not prevent God’s purpose; it became the means by which the necessary redemptive work was accomplished, securing the basis for salvation.
Les explains that because Israel rejected everything God had promised, they brought about what had to be done for our salvation—His sacrificial death, burial, and resurrection. He then contrasts believing in God with believing God, noting that believing God is faith: taking Him at His Word. The Gentiles for thousands of years did not believe God, though they may have believed in some god.