Gal 3:14, Acts 5:30-32, Acts 11:17, Gal 2:16, Eph 1:13
We have received the Holy Spirit by believing that Jesus is the Christ. (Gal 3:2-5,14, Acts 5:30-32, Acts 11:16-17, Eph 1:13)
Gal 3:2 This only would I learn of you, Received ye the Spirit by the works of the law, or by the hearing of faith? 3 Are ye so foolish? having begun in the Spirit, are ye now made perfect by the flesh? 4 Have ye suffered so many things in vain? if it be yet in vain. 5 He therefore that ministereth to you the Spirit, and worketh miracles among you, doeth he it by the works of the law, or by the hearing of faith? 14 That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.
Acts 5:30 The God of our fathers raised up Jesus, whom ye slew and hanged on a tree. 31 Him hath God exalted with his right hand to be a Prince and a Saviour, for to give repentance to Israel, and forgiveness of sins. 32 And we are his witnesses of these things; and so is also the Holy Ghost, whom God hath given to them that obey him.
Acts 11:16 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?
Eph 1:13 In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise,
A person is justified only by believing in Jesus as the Christ. (Gal 2:16)
Gal 2:16 Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified.
Those who believe that Jesus is the Christ receive the blessing of Abraham. (Gal 3:6-9)
Gal 3:6 Even as Abraham believed God, and it was accounted to him for righteousness. 7 Know ye therefore that they which are of faith, the same are the children of Abraham. 8 And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed. 9 So then they which be of faith are blessed with faithful Abraham.