Isa 42:1,6, Isa 49:6
The Old Testament prophesied that the gospel would be preached to the Gentiles. (Isa 42:1,6, Isa 49:6)
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. 6 I the Lord have called thee in righteousness, and will hold thine hand, and will keep thee, and give thee for a covenant of the people, for a light of the Gentiles;
Isa 49:6 And he said, It is a light thing that thou shouldest be my servant to raise up the tribes of Jacob, and to restore the preserved of Israel: I will also give thee for a light to the Gentiles, that thou mayest be my salvation unto the end of the earth.
The Holy Spirit came upon those who believed in Jesus as the Christ. (Acts 10:44-48, Acts 11:15-18)
Acts 10:44 While Peter yet spake these words, the Holy Ghost fell on all them which heard the word. 45 And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost. 46 For they heard them speak with tongues, and magnify God. Then answered Peter, 47 Can any man forbid water, that these should not be baptized, which have received the Holy Ghost as well as we? 48 And he commanded them to be baptized in the name of the Lord. Then prayed they him to tarry certain days.
Acts 11:15 And as I began to speak, the Holy Ghost fell on them, as on us at the beginning. 16 Then remembered I the word of the Lord, how that he said, John indeed baptized with water; but ye shall be baptized with the Holy Ghost. 17 Forasmuch then as God gave them the like gift as he did unto us, who believed on the Lord Jesus Christ; what was I, that I could withstand God? 18 When they heard these things, they held their peace, and glorified God, saying, Then hath God also to the Gentiles granted repentance unto life.