Romans 11:27 - Albert Barnes' Notes on the Bible

For this is my covenant ... - This expression is found immediately following the other in Isaiah 59:21. But the apostle connects with it a part of another promise taken from Jeremiah 31:33-34; or rather he abridges that promise, and expresses its substance, by adding “when I shall take away their sins.” It is clear that he intended to express the general sense of the promises, as they were well known to the Jews, and as it was a point concerning which he did not need to argue or reason with them, that God had made a covenant with them, and intended to restore them if they were cast off, and should then repent and turn to him. The time and manner in which this shall be, is not revealed. It may be remarked, however, that that passage does not mean that the Redeemer shall come personally and preach to them, or re-appear for the purpose of recalling them to himself; nor does it mean that they will be restored to the land of their fathers. Neither of these ideas is contained in the passage. God will doubtless convert the Jews, as he does the Gentiles, by human means, and in connection with the prayers of his people; so that the Gentiles shall yet repay the toil and care of the ancient Jews in preserving the Scriptures, and preparing the way for the Messiah; and both shall rejoice that they were made helps in spreading the knowledge of the Messiah.