It is to be noted that our Scripture reading uses the word, "mystery" three times. The word implies "a secret which is understood only by those who have been initiated into a religious sect." The word is used in the New Testament to denote "that which can only be divinely revealed to the heart and mind of man." With reference to this mystery, Paul states that:

• The mystery has been revealed to him by the grace of God - by the Spirit of God. (Ephesians 3:2-3, 7 cp. Galatians 1:11-16)
  
• His writings and ministry are designed to help other believers to understand the mystery. (Ephesians 3:3-4, 7-9 cp. Acts 26:13-20; Romans 16:25-27; II Peter 3:13-16)
  
• This mystery has not been understood in the past - it has been hidden to men's minds, since the beginning of the world, but is now revealed, by God's Spirit, unto the Apostles and prophets of the New Testament / Gospel Age. (Ephesians 3:2, 5 cp. Colossians 1:26)
  
• This mystery unlocks the unsearchable riches of Christ - unsearchable by man's natural wisdom. (Ephesians 3:8 cp. John 3:3 ["see" = with the mind]; I Corinthians 1:18-31; 2:5-16)
  
• Our mutual understanding of this mystery creates a fellowship with God and each other - a bond; a partnership in the work of the Gospel. (Ephesians 3:9 cp. Romans 1:8-12; Philippians 1:3-5; I Thessalonians 1:2-10)
  
• This mystery reveals to men God's plan to bless and unite people, from among all families of the earth (Jew & Gentile), as one spiritual body of believers in Christ. (Ephesians 3:6 cp. 2:11-22; Galatians 3:28-29; Romans 15:4-18 cp. Genesis 12:1-3.)
  
• This mystery reveals the manifold wisdom of God - a mystery, which even the angels did not know, which is being revealed to them by God's Spirit through the gospel ministry of the church! (Ephesians 3:10 cp. I Peter 1:10-12; I Corinthians 4:9; Hebrews 1:14; 13:2). See Romans 11:29-36.

The mystery of Christ, revealed in Scripture, thrills and challenges us with many a mystery. We are to learn and grow in understanding, so that we can be good stewards of God's mysteries. (II Peter 3:18; Colossians 2:1-3; 4:2-4; Ephesians 6:18-20; I Corinthians 4:1-2; I Timothy 3:8-9).

Consider:

The mystery of the Kingdom of God / Kingdom of Heaven - Matthew 13:11; Mark 4:11; Luke 8: 10
The Mystery of Iniquity - II Thessalonians 2:7
The Mystery of Christ and the Church - Ephesians 5:32