'Mystery' in the Bible

the mystery which has been hidden from ages and from generations, but has now been made manifest to his saints;

to whom God would make known what are the riches of the glory of this mystery among the nations, which is Christ in you the hope of glory:

to the end that their hearts may be encouraged, being united together in love, and unto all riches of the full assurance of understanding, to the full knowledge of the mystery of God;

praying at the same time for us also, that God may open to us a door of the word to speak the mystery of Christ, on account of which also I am bound,