Hidden and revealed

What is the word of God that Paul has a stewardship to fulfil? He defines it basically and more richly, giving both simple explanation and stirring elaboration.

It is 'the mystery' - the truths of the gospel's glorious nature and great extent known only by God's revelation.

This truth was hidden from ages and generations, grasped neither by Jew nor Gentile, till it was revealed in Christ, being made known to the saints through their participation in it: the mystery is Christ in you, the hope of glory.