25 For I do not desire, brethren, that you should be ignorant of this mystery, lest you should be wise in your own opinion, that blindness in part has happened to Israel until the fullness of the Gentiles has come in.
The “for” here explains verse 24. The mystery of God now revealed shows that God only temporarily set aside Israel as a nation. This was for the purpose that Jews and Gentiles would be incorporated into the church.
I do not desire,
Paul provided a motivation for Gentile believers to understand what God has done and will do with the nation Israel. If Gentiles understood this, they would not be proud.
Paul might have been primarily addressing Gentile believers but might also have been including Jewish believers in Rome. All are in the bonds of Christ together.
that you should be ignorant of this mystery,
The idea of Israel’s corporate stumbling for a time is a “mystery.” Why God would allow this and then restore her as a nation at some future point is difficult to understand.
A “mystery” in the biblical usage is nothing spooky. The word is not something we cannot comprehend. It is not mysterious but a truth not hitherto revealed or known. A “mystery,” then, is something previously unknown but now presently known. In this case the mystery is the union of Jews and Gentiles into the body of Christ called the church. God gave this special revelation to the apostle Paul.
Eph 3:9, and to make all see what is the fellowship of the mystery, which from the beginning of the ages has been hidden in God who created all things through Jesus Christ;
Co 1:26, the mystery which has been hidden from ages and from generations, but now has been revealed to His saints.
The “mystery” involved not only putting Israel aside but also demonstrating God’s grace to the Gentiles. This is a new dimension of God’s manifesting His glory in time.
The focus of the mystery in this verse is that Israel will be delivered as a nation after the time of Gentile salvation. Some Gentiles believed that there was no future for the nation Israel. They thought that the entire future of God’s people had to do with Gentiles. This passage refutes that idea.
lest you should be wise in your own opinion,
Paul’s readers were Gentile believers in Rome as well as Jews. He particularly wanted his Gentile readers to not be haughty about what would happen to the nation Israel during the times of the Gentiles.
that blindness [literally hardening] in part has happened to Israel
The nation of Israel’s hardening was only “in part.” God did not fully reject Israel because some believed in Jesus the Messiah when He came. We call these Jews the “remnant.”
The word “blindness” means hardening, insensibility, or obstinacy. This is a different word than used for Pharaoh’s hardening (9:18). It is also different from the word “stubbornness” (2:5). The word in this phrase refers to dullness. Continued rejection of the Word of God leads to hardening of the heart toward God.
Continued hardening of our hearts toward the Word will lead us to a state of negativity to God.
The more a believer goes negative toward what God reveals in His Word, the more negative he will be to God Himself. This happened to Israel. God revealed the Messiah to them, but they have been out of phase with God for two thousand years.