God being collectively one is similar to Adam and Eve who would "become one flesh" (Ge 2:24). "God created man in His own image . . . male and female He created them" (Gen 1:27). It is like a puzzle. Without the other piece it would be incomplete. Each piece is different and the image would not be whole unless all is pieced together. "The wife does not have authority over her own body, but the husband does; and likewise" (1Co 7:4) with the other partner. The Father, Son, and Holy Spirit are distinct yet one in nature and character. Jesus said, "'He who has seen Me has seen the Father'" (Jn 14:9). He said "'the Father is in Me, and I in the Father'" (10:38) and "'I and the Father are one'" (:30). He also prayed, "'Holy Father, keep them in Your name, the name which You have given Me, that they may be one even as We are'" (17:11). Being one also means having a single mind and purpose. Jesus prayed "'that they may all be one; even as You, Father, are in Me and I in You, that they also may be in Us, so that the world may believe that You sent Me. The glory which You have given Me I have given to them, that they may be one, just as We are one'" (Jn 17:21-22). "Do you not know . . . that you are not your own? For you have been bought with a price" (1Co 7:20).
Perhaps the Trinity is most clearly seen with all three working together with purpose. "For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: these three are one" (1Jn 5:7 KJV). The angel said to Mary, "'The Holy Spirit will come upon you, and the power of the Most High will overshadow you; and for that reason the holy Child shall be called the Son of God'" (Lk 1:35). "Now the Lord God has sent Me, and His Spirit" (Isa 48:16). In Jesus' baptism "Jesus came up immediately from the water; and behold, the heavens were opened, and he saw the Spirit of God descending as a dove and lighting on Him, and behold, a voice out of the heavens said, 'This is My beloved Son, in whom I am well-pleased'" (Mt 3:16-17). Jesus was in the water, the Father spoke from heaven, and the Holy Spirit descended like a dove. All three are present and separate. "The Spirit of the Lord God is upon me, because the Lord has anointed me" (Isa 61:1). Hebrews reports "how much more will the blood of Christ, who through the eternal Spirit offered Himself without blemish to God, cleanse your conscience?" (Heb 9:14). It is "according to the foreknowledge of God the Father, by the sanctifying work of the Spirit, to obey Jesus Christ" (1Pe 1:2). Later Jesus applied this truth by saying, "'Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit'" (Mt 28:19). He also said, "'I will ask the Father, and He will give you another Helper, that He may be with you forever; that is the Spirit of truth'" (Jn 14:16-17). Paul offered "to be a minister of Christ Jesus to the Gentiles, ministering as a priest the gospel of God, so that my offering of the Gentiles may become acceptable, sanctified by the Holy Spirit" (Ro 15:16). Paul prayed "the grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit, be with you all" (2Co 13:14).