"He that has my commandments, and keeps them, it is he that loves me: and he that loves me shall be loved of my Father, and I will love him, and will manifest myself to him ... If a man love me, he will keep my words: and my Father will love him, and we will come unto him, and make our abode with him" (John 14:21, 23).
First of all, the Bible informs us that there is only One Spirit of God who “fills heaven and earth” (Jer. 23:24) while simultaneously dwelling in true New Testament believers. Ephesians 4:4-6 states that there is only One Divine Spirit of only One Lord, “There is … One Spirit … One Lord … One God and Father of all who is over all and through all and in you all.” Hence, there cannot be two or three divine Spirits of God, but only “One Spirit.” Therefore the One Spirit of God who descended upon the virgin in Luke 1:35 is the same Spirit of the Father who also became the human spirit of the man Christ Jesus (Hebrews 1:3 says that the Son is the “substance of Being” of the Father – Hebrews 1:3) as a true man among men.
The Holy Spirit is the One Spirit of God the Father in action who later descended upon the virgin in the incarnation to become the man Christ Jesus. Hence, the Holy Spirit is the same Spirit of both the Father (God as God) and the Son (God as man). This explains why the scriptures speak of the indwelling Spirit as a single Spirit who is both the Father and the Son.
Jesus said in the gospel according to Matthew, “But when they hand you over, do not worry about how or what you are to say; for it will be given you in that hour what you are to say. For it is not you who speak, but it is the Spirit of your Father who speaks in you.” Matthew 10:19-20
Jesus said in the gospel according to Luke, “When they bring you before the synagogues and the rulers and the authorities, do not worry about how or what you are to speak in your defense, or what you are to say; for the Holy Spirit will teach you in that very hour what you ought to say.” Luke 12:11-12
Then Luke goes on to record Jesus saying, “… they will lay their hands on you and will persecute you, delivering you to the synagogues and prisons, bringing you before kings and governors for My name’s sake. It will lead to an opportunity for your testimony. So make up your minds not to prepare beforehand to defend yourselves; for I will give you utterance and wisdom which none of your opponents will be able to resist or refute.” Luke 21:12
Notice that all three passages of scripture say that the indwelling Spirit will give New Testament believers the words to speak when being delivered up before rulers and magistrates. Matthew 10:19-20 says the indwelling “Spirit of your Father who speaks in you.” Luke 12:11-12 says the indwelling “Holy Spirit will teach you… what you ought to say.” And in Luke 21:12 Jesus said, “I will give you utterance and wisdom which none of your opponents will be able to resist or refute.”
All three parallel passages are similar, except that the indwelling Holy Spirit is described as the same Spirit of the Father and the Son. Here the Oneness Modalistic understanding best fits the scriptural evidence. For Arians and Socinians cannot explain how the indwelling omnipresent Spirit can be Jesus Christ without acknowledging Jesus Christ as the Spirit of God (Romans 8:9), while Trinitarians cannot explain how the Father, Holy Spirit, and Christ Jesus can speak as the same Divine Person. Therefore, only the Oneness doctrine brings harmony to all of the scriptural data.
If we are to truly believe that God the Father really became a man, then we would expect that the human spirit of Christ, who was formed “out of the Holy Spirit” (“ek” = “out of” - Matthew 1:20) of the Father within the virgin would later become the indwelling Spirit within the hearts of New Testament believers. This explains why Galatians 4:6 specifically calls the indwelling “Spirit of truth” (John 14:17), “the Spirit of His Son” residing “in our hearts” who “intercedes for the saints” (Romans 8:27) “crying Abba Father” (Gal. 4:6). This further explains why the Holy Spirit is called “the Paracletos” (the Advocate and Intercessor) in John 14:26, while John 14:16-18 and 1 John 2:1 calls Jesus “the Paracletos” (the Advocate and Intercessor). Therefore the “we” and the “our” in John 14:23 are not two coequally distinct divine spirit persons of a three person deity, but rather, “the Spirit of God” (Rom. 8:9) is the Holy Spirit of the Father who also became the human spirit of His Son by also becoming a man via virgin conception and birth.
Jesus could say “we will come unto him, and make our abode with him” because the One God who is the Father also manifested Himself in the flesh (1 Tim. 3:16) to become a true human son (Heb. 2:17). Thus, there are two primary manifestations of God: God as the Father and God the Father with us as the Son because there are two distinct manifestations of God after the Holy Spirit of God also became a man through the virgin conception. Therefore the indwelling Holy Spirit is the Spirit of both the Father (God as God) and the Son (God as man). For God as God is the same Divine Spirit who also became a man (God as man). This explains why Romans 8:9, 26, 27, and 34 state that the indwelling Spirit of God is the Spirit of Christ, who makes intercession for the saints according to the will of God (See Hebrews 7:25).
“However, you are not in the flesh, but in the Spirit, if indeed the Spirit of God dwells in you. But if anyone does not have the Spirit of Christ, he does not belong to Him.” Romans 8:9 NASB
Notice that the inspired text states that the indwelling “Spirit of God” who descended upon the virgin (Luke 1:35 “the Holy Spirit will come upon you”; Matthew 1:20 “the child who has been conceived in her is OF THE HOLY SPIRIT”) is the same “Spirit of Christ” because the Spirit of God also became a man through the virgin.This explains why we see two manifestations of the Spirit of God in New Testament Scripture: the unchangeable Father outside of the incarnation, and His new manifestation as that same “God” “manifested in the flesh, justified in the Spirit…” (1 Tim. 3:16) who “shared in our humanity” to be “made fully human in every way” (Heb. 2:14, 17 NIV).
When the human spirit of Christ ascended into heaven, the new human aspect of His existence became the “life giving Spirit” (1 Corinthians 15:45) who “ascended far above all the heavens, so that He MIGHT FILL ALL THINGS” (Ephesians 4:10).God as God has always filled all things, but God’s new manifestation as “God with us” as a true man did not fill all things until the man Christ Jesus ascended into heaven to become omnipresent like the Father.
“…the Spirit also helps our weaknesses, for we do not know how to pray as we should, but the Spirit Himself intercedes for us with groanings too deep for words; and He who searches the hearts knows what the mind of the Spirit is, because He intercedes for the saints according to the will of God.” Romans 8:26-27 NASB
“Christ Jesus is He who died, yes, rather who was raised, who is at the right hand of God, who also intercedes for us.” Romans 8:34 NASB
Arians and Unitarian Socinians cannot explain how the Holy Spirit of God can indwell New Testament believers to make intercession to the Father because angels (Arianism – Jehovah’s Witnesses) and mere men (Socinianism) cannot be omnipresent in filling the heavens and the earth like God (Jer. 23:24) without violating Isaiah 46:9.For the only true God has said, “I am God and there is none else; I am God and THERE IS NONE LIKE ME” (Isaiah 46:9). Jehovah’s Witnesses teach that the Holy Spirit is an impersonal “active force,” but how can an impersonal force “intercede” (“the Spirit Himself intercedes for us” Rom. 8:26) while having a “mind” (“the mind of the Spirit” Rom. 8:27) and being called a “He” in Romans 8:27 (“He intercedes for the saints according to the will of God” – Rom. 8:27)?
Moreover, Trinitarian theologians cannot explain how an alleged non-incarnate God the Holy Spirit Person can be said to “intercede” to God (Rom. 8:26-27) while remaining coequal. John 14:26 clearly calls the Holy Spirit the “Paraclete” (which means advocate or intercessor), but John 14:16-18 and 1 John 2:1 inform us that Jesus is the “Paraclete” who “advocates” and “intercedes” for us. Hence, Trinitarians have two mediators, two advocates, and two intercessors while the scriptures state that there is only one mediator who advocates and intercedes for the saints to our Heavenly Father (Hebrews 7:25; 1 Tim. 2:5).
When the Spirit of the only true God also became a man, he infused humanity into His deity by incarnating Himself as a man while remaining the unchangeable Holy Spirit who fills heaven and earth (Jer. 23:24). Therefore, the scriptures prove that the human spirit of Christ is that spirit who descended into Hades (Matthew 12:40 / Ephesians 4:9), took the keys of death and hell (Revelation 1:18), and then resurrected his own body (John 2:19). After the resurrection, he ascended up to heaven that he "might fill all things" (Ephesians 4:10) as the “life giving” omnipresent Holy Spirit (1 Corinthians 15:45).
Wherefore, the scriptures teach true Monotheism in that there is only One Divine Spirit of our Heavenly Father who seeks true worshipers to worship Him “in Spirit and in truth” (John 4:23-24). For the God who “is a Spirit” (John 4:23) is “the Father” who seeks “true worshipers” to worship Him “in Spirit and in truth” (John 4:23-24). Hence it was the same Holy Spirit of the Father who descended upon the virgin Mary to also become a man in order to save us as “the arm of Yahweh” Himself revealed (Isaiah 53:1). This explains why “the Spirit of Christ” is identified as the same “Spirit of God” (in Romans 8:9) who came to save us as a true man.
The scriptures prove that the One Spirit of God (John 4:23-24; Ephesians 4:4-6) is the indwelling Holy Spirit of the Father who is that Spirit who also became the Son (“the Lord is the Spirit” 2 Cor. 3:17; “Christ Jesus the Lord” 2 Cor. 4:5). Hence, the indwelling Holy Spirit is the same divine identity as the Father (God as God) and the Son (God as man). For true New Testament believers know God as God outside of His incarnation as our Heavenly Father, while also knowing God inside of His incarnation as the Son, whose indwelling Holy Spirit “intercedes for us with groans too deep for words” (Romans 8:26-27).