This was in accordance with the eternal purpose which He carried out in Christ Jesus our Lord,Ephesians 3:11(NASB)
The mystery of the Church was in God's heart and mind from the beginning, but there was a special reason why the Lord kept the 'dispensation of the grace of God' a secret during his earthly ministry. Indeed, it was kept hidden from ages and generations - and cleverly concealed from angelic beings, invisible powers, and the prince of the power of the air.
The formation of the Church, which is the Body of Christ, is a wisdom which none of the angelic rulers of this age knew about, nor did they understand the significance of Christ's humanity, His sinless life, and His sacrificial death - until after his Resurrection. For if they had understood God's purpose and plan, they would never have crucified the Lord of glory - but in so doing, they unleashed the grace of God upon humankind and across the farthest corners of the universe.
The disclosure of this mystery was given by revelation to the apostle Paul for our learning - but not for our learning alone. This mystery was given to demonstrate the manifold wisdom of God to the invisible, angelic hosts in heavenly places. The Lord is the ultimate teacher and the mystery, which is the Church, is an object lesson of the unsearchable wisdom of God to both the holy angels of God and fallen spirits alike.
The Lord Jesus triumphed over sin, Satan, death, and hell, in order to demonstrate God's manifold wisdom, might, majesty, dominion, glory, and grace to the angelic hosts. It is humanity that has been redeemed and not angels - and yet they look on in wonder, as they see the Lord redeeming the fallen race of sinful man which rebelled against Him in the garden of Eden.
They witnessed the tremendous cost that God paid to prepare a Bride for His Son - i.e. the shedding of Christ's human blood on our account. They discovered that in addition to our position in Christ and the forgiveness of sins, we have been blessed with every spiritual blessing in Christ. And they came to understand that Satan was defeated, Christ was victorious, and the Church, which is His Body, has been enthroned in heavenly places in Christ - and has been promised an inheritance which is kept for us in heaven.
Every aspect of God's amazing plan of redemption that is received by faith in Christ's sacrificial death and His glorious Resurrection, was "in accordance with the eternal purpose and plan of God, which was hidden for ages and generations... but which God finally carried out in Christ Jesus our Lord."
God is omniscient and knew that man would be tempted of Satan and fail to obey His instructions... and so God in His grace, forged the plan of redemption before the creation of the world. However, God in His wisdom, kept His Christ-centred secret from the principalities and powers. Christ's incarnation, death, burial, resurrection, ascension and glorification.. together with the creation of the Church, which is His Body, were kept under wraps so that Jews and Gentiles alike could be saved by grace through faith in Him - and become part of His spiritual Body on earth.
God's plan of redemption was kept hidden, for they would not have crucified Christ if they had understood the far-reaching effects of His redemptive plan. God's plan has now been made known "so that in the ages to come He might show forth the surpassing riches of His grace, in His kindness toward us - in Christ Jesus our Lord."
Heavenly Father, what a glorious plan of redemption and what manifold wisdom - that Your plan of salvation should be kept hidden from the enemy of our soul so that he was unable to interfere with the triumph of the Cross, the glory of the Resurrection, and the mystery of the indwelling Holy Spirit within the Christian Church, which is the eternal Body of Christ. Thank You that I am part of that redeemed company who, in the ages to come, will show forth Your immeasurable glory and over-abounding grace, to Your praise and glory. Thank You, in Jesus' name, AMEN.