Isa 11:1-2, Isa 42:1
In the Old Testament it was foretold that the Holy Spirit would come upon Christ. (Isa 11:1-2, Isa 42:1, Isa 61:1)
Isa 11:1 And there shall come forth a rod out of the stem of Jesse, and a Branch shall grow out of his roots: 2 And the spirit of the Lord shall rest upon him, the spirit of wisdom and understanding, the spirit of counsel and might, the spirit of knowledge and of the fear of the Lord;
Isa 42:1 Behold my servant, whom I uphold; mine elect, in whom my soul delighteth; I have put my spirit upon him: he shall bring forth judgment to the Gentiles.
Isa 61:1 The Spirit of the Lord God is upon me; because the Lord hath anointed me to preach good tidings unto the meek; he hath sent me to bind up the brokenhearted, to proclaim liberty to the captives, and the opening of the prison to them that are bound;
The Holy Spirit came upon Jesus to come upon Christ. This means that Jesus is the Christ. (Lk 3:21-22)
Lk 3:21 Now when all the people were baptized, it came to pass, that Jesus also being baptized, and praying, the heaven was opened, 22 And the Holy Ghost descended in a bodily shape like a dove upon him, and a voice came from heaven, which said, Thou art my beloved Son; in thee I am well pleased.