Who was the mystery to be made known to?
The mystery was to be made known to all men—the whole human race—not just Israel or the Gentiles alone. Paul was to make all men see the fellowship of the mystery, which had been hidden in God from the beginning of the world.
Les explains that God had the Gentiles on His mind, but the revealing of the mystery was not limited to them. Paul says he was made a minister to make all men see the fellowship of the mystery, the secret hidden in God from the beginning of the age. It was not just Israel, nor just the Gentiles, but the whole human race. Les also notes another aspect of the mystery: Israel would be spiritually blinded for almost two thousand years, and the Gentiles would come into a privileged position with Israel's God in the body of Christ.
And to make all men see what is the fellowship of the mystery, which from the beginning of the world hath been hid in God, who created all things by Jesus Christ: