Jesus said, “I am in the Father and the Father is in me” (John 14:1). How is Jesus “in” the Father? This scripture could not be teaching that Jesus is physically inside the Father because Jesus was on earth when he said this. We know God dwells in heaven on His throne. 

How was God “in” Jesus? Again, this can’t mean the heavenly Father was literally inside Jesus. A human body could not possibly contain God. But God can be in Jesus’ mind and heart. Their union is a union of purpose. Jesus talked about how closely he followed his Father’s will in John 6:38, “For I came down from heaven, not to do mine own will, but the will of Him that sent me.” Hebrews 10:9, “Then said he, Lo, I come to do Thy will, O God.” 

Additionally, Jesus said the works he performed and even his very words were all from God. John 14:10, “The words that I speak unto you I speak not of myself: but the Father that dwelt in me, He doeth the works.” 

Jesus wanted his followers to share in this wonderful unity. “I am in the Father, and ye in me, and I in you.” John 14:20. Does this show believers are the third entity of a trinity? No.

God and Jesus are both dwelling “in” us when we try to do and obey God’s will. “Jesus answered…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.” It is when we study the Bible and transform our characters by applying these truths to our lives that we are “living in” him, and God and Jesus are “living in” us.

It may be helpful to remember times when we have sinned, when we feel sorrow, disappointment, even shame, as we are distanced from God. Likewise, when we are living in obedience to God’s will, we feel communion and closeness with Him. This is the experience of oneness.

The holy spirit is God’s divine power and influence. It is called in the Scriptures by many different titles: “The Spirit of God,” “The Spirit of the Father,” “the Spirit of Christ,” “the Spirit of Holiness,” “The Spirit of Truth,” “The Spirit of a Sound Mind,” “The Spirit of Liberty,” “The Holy Spirit of Promise,” “The Spirit of Meekness,” “The Spirit of Understanding,” “The Spirit of Wisdom,” “The Spirit of Glory,” “The Spirit of Counsel,” “The Spirit of Grace,” “The Spirit of Adoption” and “The Spirit of Prophecy.”

These various titles are expressions of the influence and power of God. It is only through the power of the holy spirit that we are able to be united as the body of Christ, “For by one Spirit are we all baptized into one body” (1 Corinthians 12:13). We are united with God and Jesus in purpose. “For as many as are led by the Spirit of God, they are the sons of God” (Romans 8:14).

The word “trinity” does not appear in the Bible, and trinitarians to not all agree on exactly what it means. However, as shown above, there are many verses which illustrate the unity of God the Father with Jesus, His only begotten son, and the church (the true followers of Jesus). They are united in purpose of heart, mind, and works through the power of the holy spirit. 

Additional Resources: 
PDF booklet: The Lord Our God is One Lord
PDF booklet: The Holy Spirit

Christian Questions Podcast
Episode #1325: “Does God’s Holy Spirit Speak to Us?”
Unfolding how the holy spirit does and does not function in our lives
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CQ Rewind Show Notes