by Michael R. Burgos Jr.
While the cults often characterize the Holy Spirit as an impersonal force, or as God the Father, Scripture teaches that the Holy Spirit is both God and a distinct person from God the Father. While many passages could be drawn upon to demonstrate the distinct personhood and deity of the Holy Spirit, for sake of brevity I will cite only three.
1. 2nd Corinthians 13:13:
The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all. (2 Corinthians 13:13)
In this doxology, Paul commends the κοινωνία (koinōnia) of the Holy Spirit to the Corinthians—a term which is defined as “close association involving mutual interests and sharing, association, communion, close relationship.” A similar sentiment is communicated at 1 John 1:3, only there, the κοινωνία is said to be had “with the Father and with his Son Jesus Christ.” Hence, just as one may have fellowship with the Father and Son, one may have fellowship with the entirely personal Holy Spirit.
Some non-trinitarian interpreters have argued that “the fellowship of the Holy Spirit” actually refers to “the fellowship that Christians have with each other because of the presence of God’s gift, holy spirit.” However, the genitival construction ἡ κοινωνία τοῦ ἁγίου πνεύματος precludes such an understanding. This “fellowship” is quite literally “the Holy Spirit’s” fellowship, and not the fellowship had between fellow Christians.
2. Matthew 28:19:
Jesus came and said to them, "All authority in heaven and on earth has been given to me. Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.” (Matthew 28:18-19)
καὶ προσελθὼν ὁ Ἰησοῦς ἐλάλησεν αὐτοῖς λέγων· ἐδόθη μοι πᾶσα ἐξουσία ἐν οὐρανῷ καὶ ἐπὶ [τῆς] γῆς. πορευθέντες οὖν μαθητεύσατε πάντα τὰ ἔθνη, βαπτίζοντες αὐτοὺς εἰς τὸ ὄνομα τοῦ πατρὸς καὶ τοῦ υἱοῦ καὶ τοῦ ἁγίου πνεύματος. (Matthew 28:18-19, NA28)
First, it must be noted that while some non-trinitarians have argued that the text of Matthew 28:19 is an interpolation, every single known ancient Greek and versional manuscript that contains the relevant passage contains the three-part formula as it appears above. Many non-trinitarians have argued that Eusebius cites an alternate reading. However, the alleged Eusebian variant doesn't actually mention baptism, but rather the making of disciples "in my name." So too, Eusebius himself cites the three-part formula several times. Thus, to discard a text that has universal attestation among manuscripts for an otherwise unattested reading from a commentator is untenable.
When three articular nouns of the same case are connected by the copulative καὶ (i.e., and), each noun expresses "a different person, thing, or quality from the preceding noun." There are exceptions to this rule, but only when the context of the passage explicitly makes clear that one person is under consideration. The nouns Father, Son, and Holy Spirit are articular and in the genitive case. Since the other two names within the text are persons, namely the Father and Son, it naturally follows that the Holy Spirit is a different person than the Father and Son.
How then do we understand passages like Acts 2:38 wherein Peter told his audience, “Repent and be baptized every one of you in the name of Jesus Christ”? That is, is Peter introducing a contrary oral invocation for baptism? Certainly not. Rather, Peter was commanding people “in the name of Jesus Christ” to be repent and be baptized. This reading of the text better explains why both repent and baptism are to be done in Jesus’ name, and the other places within Acts where Jesus' name is utilized in the commission of a healing or exorcism. When Paul commands the spirit to come out of the possessed girl in Acts 16:18, he stated, "I command you in the name of Jesus Christ to come out of her." When Peter healed the beggar in Acts 3:6, he stated, "In the name of Jesus Christ of Nazareth, rise up and walk!" Therefore, in the same way that people are exorcized and healed "in the name of Jesus," Peter commanded the crowd in Acts 2:38 to repent and be baptized in the name of Jesus. 
3. Hebrews 10:15:
And the Holy Spirit also bears witness to us; for after saying, “This is the covenant that I will make with them after those days, declares the Lord: I will put my laws on their hearts, and write them on their minds.” then he adds, “I will remember their sins and their lawless deeds no more.” (Hebrews 10:15)
Within in the above text, the writer to the Hebrews quotes the Septuagint’s rendering of Jeremiah 31:1-34. Therefore, for the author of Hebrews, the Holy Spirit is the Septuagintal Lord (Ὁ κύριός) and subsequently Yahweh (יְ הוָה). Thus, if Yahweh is a person, then the Holy Spirit is a person, because the Holy Spirit is Yahweh.
 F. W. Danker, A Greek-English Lexicon of the New Testament and Other Early Christian Literature, 3rd Ed., (Chicago: Chicago Univ. Press, 2000), 552.
 See Contra Marcellum I.1.9; I.1.36; Theologia III. 5.22; Caesarea 3 (Socrates, Ecclesiastical History 1.8); Psalms 117.1-4; and Theophania 4.8.
 Sharp, Granville, Remarks on the uses of the Definite Article in the Greek Text of the New Testament; Containing Many New Proofs of the Divinity of Christ form Passages which are Wrongly Translated in the Common English Version, 3rd Ed., (London: Vernor and Hood, 1803), 14. See also Wallace, Daniel B., Granville Sharp’s Canon and Its Kin: Semantics and Significance, (New York: Peter Lang, 2009), 49-50.
 e.g., Revelation 1:17-18.
 cf. 1 Thess 3:6.
 cf. Deut 21:5.