Galatians 6:16, "And as many as walk according to this rule, peace be on them, and mercy, and upon the Israel of God.
Some believe in replacement theology. The church is the new Israel and is now the recipient of all the promises made to Israel. They seem to reject the promises made to the Old Testament prophets and the very teaching of Jesus and the teachings in the New Testament.
(See Isa. 11:10-11; Zech. 8:1; Micah 4; Jer. 31:35-36; Acts 1:6-9; Rom. 9-11:25, 28; Rev. 20:4-6).
Israel of God means all Jewish believers in Christ who are both physical and spiritual descendants of Abraham.
(See Galatians 3:7, 18; Romans 2:28-29; 9:6-7).
While some believe that "Israel of God" is the church, the evidence does not support such a conclusion. First, the repetition of the preposition ("upon" or "to") indicates two groups are in view. Second, all the 65 other occurrences of the term "Israel" in the New Testament refer to Jews. It would thus be strange for Paul to use "Israel" here to mean Gentile Christians. Third, Paul elsewhere referred to two kinds of Israelites - believing Jews and unbelieving Jews (cf. Romans 9:6). Lest it be thought that Paul is anti-Semitic, he demonstrated by means of this benediction his deep love and concern for true Israel, that is, Jews who had come to Christ. Fourth, the Israel of God refers to those Jews by natural births who receive the Lord Jesus as Messiah. There was neither peace nor mercy for those who walked under the law, but both are the portion of those in the new creation.
God has a plan for the church and for Israel with two distinct programs but both come to Jesus by grace through faith.