'Mystery' in the Bible

the mystery [which] has been hidden from the ages and from the generations, but has now been revealed to his saints,

to whom God wanted to make known what [is] the glorious wealth of this mystery among the Gentiles, which is Christ in you, the hope of glory,

so that their hearts may be encouraged, united in love and into all the wealth of the full assurance of insight into the knowledge of the mystery of God, Christ,

praying at the same time for us also, that God may open for us a door of the message, to speak the mystery of Christ, for which also {I am a prisoner},