The second glorious mysterious Union is that of God the Son with human flesh. The Apostle John so wonderfully describes this in John 1:14, "And the Word became flesh and dwelt among us, and we beheld His glory, the glory as of the the Only Begotten of the Father, full of grace and truth." And again in I John 1:1, "that which was from the beginning (John 1:1) which we have heard, which we have seen with our eyes, Which we have looked upon, and OUR HANDS HAVE HANDLED concerning THE WORD OF LIFE." Hebrews 2:14 "Inasmuch then as the children have partaken of flesh and blood, HE HIMSELF likewise shared in the same, that through death He might destroy him who had the power of death, that is the devil." Astoundingly, the Eternal Son of God became wedded to our flesh in that Perfect Body prepared for Him (Hebrews 10:5-10), bore the punishment due our sin, was crucified, buried, and risen to ascend to the Right Hand of the Father--as our Man! He now lives in the Holy Presence as the Living Intercession for us, assuring our rightful residence in that Presence! WOW!!
The third mysterious union is that of the union of the redeemed of God with the Son of God through His Incarnation as the Son of Man. We are united inseparably with the Son of God Who is the Son of Man, that we may bask in the same Eternal Love that has been God from before the beginning! In our Lord's High Priestly prayer in John 17:20-21, Jesus prays, "I do not pray for these alone (the Apostles) but for those who will believe in Me through their word; that they all may be one, as You, Father are in Me, and I in You; that the world may believe that You sent Me." Vs 23 "I in them, and You in Me; that they may be made perfect in one, that the world may know that You have sent Me and loved them as You have Loved Me." Be careful! We are not made gods as some distortionists claim! No, we are united inseparably with the Sent One, the Son of God/Son of Man that we may behold His Glory, and bask in that Glory which is the Love that the Son had from the Father from before the beginning. Vs 24 "Father, I desire that they whom You gave Me may be with Me where I am, that they may behold My glory which You have given Me; for You Loved Me before the foundation of the world." This has been the Father's will and purpose from all eternity! Ephesians 1:9-11 "...having made known to us the mystery of His Will, ACCORDING TO HIS GOOD PLEASURE, WHICH HE PURPOSED IN HIMSELF, that in the dispensation of the fullness of the times, He might gather IN ONE all things IN CHRIST, both which are in heaven and which are on earth IN HIM (The Christ), IN WHOM also we have obtained an inheritance, being predestined ACCORDING TO THE PURPOSE OF HIM WHO WORKS ALL THINGS ACCORDING TO THE COUNSEL OF HIS OWN WILL." Personally, I am very thankful for His Will! Mine is fallen, dead, and would never have been a part of the "ingathering" had it not been for His Will! "If any man be IN CHRIST, he is a new creature, old things are passed away; behold, all things are become new." II Corinthians 5:17 Simply, this mysterious union means that Father has made a way that He can Love fallen, yet redeemed creatures with exactly the same Love which He has poured out on His Son from all eternity! Not just the same kind of love, but the Very Same Love, we being caught up in the Beloved, into the very Bosom of the Father!