What does 'blindness in part' mean when it is said to happen to Israel?
It means Israel’s spiritual blindness is temporary, not permanent or final. It lasts only for a segment of time—until the fullness of the Gentiles is brought in. When the body of Christ is complete and the church is removed, Israel’s blindness will end and they will again have spiritual relationship with Jehovah God.
Les explains that this spiritual blindness was a secret or mystery kept in the mind of God, not found elsewhere in Scripture. Isaiah spoke of Israel being blinded and unable to hear, but Isaiah did not connect that blindness to a period when God would turn to the Gentiles. The mystery now revealed is that 'blindness in part' means not forever, but for a segment of time—it has happened to Israel 'until.' It is not final; it will end someday. That end comes when the fullness of the Gentiles has been brought in—the body of Christ. When the body of Christ is finally filled, the last person saved, and the church is removed (the rapture), God will pick up where He left off with Israel, the Jew. Then their spiritual blindness will more or less come to an end, and they will again have a spiritual relationship with their Jehovah God. Les also notes Jesus' 'untils' in Matthew 23, where Israel would not see Him and He would be moved from their midst and return to glory.