'Secret' in the Bible

This secret was hidden throughout the ages and generations but has now been revealed to his saints,

to whom God wanted to make known the glorious riches of this secret among the gentiles which is the Messiah in you, our glorious hope.

At the same time also pray for us that God would open before us a door for the word so that we may tell the secret about the Messiah, for which I have been imprisoned.