"In that day you will know that I am in My Father, and you in Me, and I in you.John 14:20(NASB)
Jesus had just finished telling His confused disciples that He was going away to prepare a place for them in His Father's house, but that He would not leave them comfortless but send the Holy Spirit to be with them and to live inside them. Their bodies were to become God's holy temple, His permanent residence, and although they did not know it, Pentecost was on the near horizon.
The disciples must have been overwhelmed with the speed with which things took place in those last few days before Christ's crucifixion. They believed He would overthrow the Romans and set up His eternal kingdom as Scriptures foretold. Had they not been preaching this for the last three years? "Turn from your sins.. Jesus is the Messiah. He is the King of Israel.. the kingdom of heaven is at hand and we're going to sit on 12 thrones." YES - there was much they did not yet understand.
They would have to learn that the kingdom was to be delayed for a time. They had to discover that Gentiles and Jews were to become one Body in Christ. They were to learn of the hidden mystery, which was given to Paul: "Which is Christ in You the hope of glory." YES, there was much that they would have to learn from the apostle Paul in the early years of the Christian Church, but they could not bear it at this time as the Cross loomed ever closer.
Jesus had told them that the Holy Spirit would be sent to them from Father after His departure (and we know that He came at Pentecost). And Christ expanded this exciting truth by telling them: "In that day, you will know that I am in My Father, and you in Me, and I in You." But the mountain of 'Church age' doctrine that Christ started to share with them following His rejection as Israel's Messiah was overwhelming to these confused men, much of which they would not be understood until later - when many Church age mysteries were revealed to Paul.
They would soon discover the astonishing truth of our permanent union with Christ and that His resurrected life would be imputed to all believers so that instead of being influenced by the old Adamic nature, we would receive a new nature - the resurrected life of Christ. No surprise that the disciples could not bear these identification truths at that time for like us, they had to discover the inability of the old self life and that only the new life in Christ, which we all receive at Salvation can live a godly life.
In that day Christ told them, when I have gone to be with my Father, you will receive the promise of the Father (the indwelling the Holy Spirit) Who is with you now but He will be IN you as a Witness that I am in My Father (in union with Him).
In that day when the Church is born and the Spirit is sent, Jesus told them, you will know that you are in Me (i.e. positioned in Christ - baptised into His Body - united with Him in spirit and truth - born again and covered in Christ's own righteousness - a branch of the True Vine.. seated with Him in heavenly places - accepted in Christ and positioned in HIM)
In that day, when you are in-dwelt by the Holy Spirit; placed into the Body of Christ and sealed - He told them, you will also know that I am in you (My resurrected life given to you - My eternal life imparted to you - My perfect life imputed to you) so that I may influence your choices and decisions, until it is not I that lives, but Christ that lives in me.. YES.. in that day you will know that I am in My Father, and you in Me, and I in you
Heavenly Father, thank You for Your Word of truth, my new life in Christ, and the indwelling Spirit of God. Thank You that I am in Christ and He in Me. I pray that I may abide in Him and He in me so that the life that I now live in this body and the choices that I make as I journey through life, may come from my new nature, as prompted by the Holy Spirit, to Your praise and glory. May I grow in grace and in a knowledge of You, day by day. This I ask in Jesus' name, AMEN.