He made known to us the mystery of His will, according to His kind intention which He purposed in HimEphesians 1:9(NASB)
The coming of the Messiah was no hidden mystery for it was foretold by the prophets of Israel, but God had kept secret one peculiar aspect of His marvellous plan, which He had purposed in Himself before the world was created.
The mystery, that was kept hidden from men and angelic beings alike, was that the unsearchable riches of God's grace, which He purposed towards whosoever would trust in His only begotten Son (whether Jew or Gentile, male or female, old or young bond or free), were to become part of the mystical Body of Christ, which is the Church.
It was Paul to whom this great secret was revealed - that the Church, which is the Body of Christ, were to become God's heavenly people, while the nation of Israel will one day be restored as God's earthly people. The 'heavenly people' are to engage in a spiritual war, to demolish spiritual strongholds in high places so that God's 'earthly people' may receive the earthly inheritance promised to Abraham, Isaac, and Israel.
God in His wisdom and kindness, determined to keep the Church a mystery, for had Satan and his demonic forces known that God's plan was to secure back His heavenly realm by means of the Church, they would not have crucified the Lord of Glory.
Praise God that we who trust in Jesus are the joyous recipients of this marvellous mystery that was kept hidden in ages past, but now has been revealed to us through the apostle Paul: "According to His pleasure, which God purposed in Himself, that in the dispensation of the fullness of times He might gather together all things - IN CHRIST."
Heavenly Father, You are a good and gracious God, and Your plans and purposes are perfect. Help me to confidently surrender all my own plans and purposes into Your hands, for Your will is perfect and Your wisdom is without bounds. In Jesus' name I pray, AMEN.