In John 14:2 the Lord Jesus began to speak about our dwelling place in God. In John 14:20 He said, “In that day you will know that I am in My Father, and you in Me, and I in you” and in John 15:4 He said, “Abide in Me and I in you.” This is a mutual abiding—we dwell in the Triune God and the Triune God dwells in us. The Lord’s unveiling of this reality continues in John 17. In verse 21 He prayed, “You, Father, are in Me and I in You, that they [the believers in v. 20] also may be in Us.” Here we are in the Triune God. Then in verse 23 He continued, “I in them, and You in Me.” Here the Triune God is in us.
This mutual abiding is also presented in the epistles. Romans 8:1-2 say that we “are in Christ Jesus;” verse 10 declares, “Christ is in you.” In Romans 8 we see the practicality of “Abide in Me and I in you.” The key is our human spirit. In the first part of Romans 8 our spirit is life because Christ is in us—this is unvarying; our mind however is variable—it may be of/on the flesh (resulting in death) or of/on the spirit (resulting in life and peace) (v. 6); our body is dead because of sin yet it can receive life (v. 10-11).
Our spirit is the unvarying part of our being, it is life (eternal life), and it is one with the indwelling Spirit (v. 16). Therefore, we walk and have our being according to the Spirit mingled with our spirit (v. 4-5). The Spirit wants to dwell in us, to live in us and to have us let His living become our living. This mutual living is a foretaste of the mutual abiding of the Triune God and His people in New Jerusalem.