Our Lord promised this intimate relationship when He returned to heaven.
I will not leave you as orphans; I will come to you. Yet a little while and the world will see Me no more, but you will see Me. Because I live, you also will live. In that day you will know that I am in My Father, and you in Me, and I in you. Whoever has My commandments and keeps them, he it is who loves Me. And he who loves Me will be loved by My Father, and I will love Him and manifest Myself to Him. … If anyone loves Me, he will keep My word, and My Father will love Him, and We will come to Him and make Our home with Him (John 14:18-23).
This promise was initially made to the apostles, but Revelation 3:20 makes a similar promise to repentant Christians: “If anyone hears My voice and opens the door, I will come in to him and eat with him, and he with Me.” The Son is enthroned in heaven with the Father. How, then, do they dwell with obedient humans? As the New Testament develops this theme, the answer becomes clear: The Father and the Son live with and in obedient believers through their one Spirit (Romans 8:8-11, 15, 23; Ephesians 2:22; 3:14-17; 4:4). Speaking of the Christian’s physical body, Paul writes,
Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, for you were bought with a price. So glorify God in your body (1 Corinthians 6:19-20 cf. Romans 8:11).
“Your body is a temple of the Holy Spirit within you.”
Speaking of the Christian’s inner being, Paul writes,
And because you are sons, God has sent the Spirit of His Son into our hearts, crying, “Abba! Father!” (Galatians 4:6 cf. 1 Thessalonians 4:8; 2 Timothy 1:14; Hebrews 6:4).