Jesus Christ is the true Israel, and those indwelt by His Spirit are the true Israel of God.
Galatians 6:15-16 For in Christ Jesus neither circumcision availeth any thing, nor uncircumcision, but a new creature. And as many as walk according to this rule, peace be on them, and mercy, and upon the Israel of God.
Isaiah 49:3 And said unto me, Thou art my servant, O Israel, in whom I will be glorified.
John Wesley’s Commentary:
O Israel-As the name of David is sometimes given to his successors, so here the name of Israel may not unfitly be given to Christ, not only because he descended from his loins; but also because he was the true and the great Israel, who, in a more eminent manner, prevailed with God, as that name signifies, of whom Jacob, who was first called Israel, was but a type.