The Spirit of Christ in the Old Testament …
1 Peter 1:9-11 Receiving the end of your faith, even the salvation of your souls. Of which salvation the prophets have enquired and searched diligently, who prophesied of the grace that should come unto you: Searching what, or what manner of time THE SPIRIT OF CHRIST WHICH WAS IN THEM did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow.
1 Corinthians 10:1-4 Moreover, brethren, I would not that ye should be ignorant, how that all our fathers were under the cloud, and all passed through the sea; And were all baptized unto Moses in the cloud and in the sea; And did all eat the same spiritual meat; And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: AND THAT ROCK WAS CHRIST.
Deuteronomy 18:18-19 I will raise them up A PROPHET from among their brethren, like unto thee, and will put my words in his mouth; and he shall speak unto them all that I shall command him. And it shall come to pass, that whosoever will not hearken unto my words which he shall speak in my name, I will require it of him.
Acts 3:18-26 But those things, which God before had shewed by the mouth of all his prophets, that Christ should suffer, he hath so fulfilled. And he shall send Jesus Christ, which before was preached unto you: Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began. For Moses truly said unto the fathers, A PROPHET shall the Lord your God raise up unto you of your brethren, like unto me; him shall ye hear in all things whatsoever he shall say unto you. And it shall come to pass, that every soul, which will not hear that prophet, shall be destroyed from among the people. Yea, and all the prophets from Samuel and those that follow after, as many as have spoken, have likewise foretold of these days. Ye are the children of the prophets, and of the covenant which God made with our fathers, saying unto Abraham, And in thy seed shall all the kindreds of the earth be blessed. Unto you first God, having raised up his Son Jesus, sent him to bless you, in turning away every one of you from his iniquities.
There is only one true Israel of God. Believers in Christ have not replaced, but rather they have been joined to the commonwealth of Israel.