'Mystery' in the Bible

having made known to us the mystery of his will, according to his good pleasure which he purposed in himself

that by revelation the mystery has been made known to me, (according as I have written before briefly,

by which, in reading it, ye can understand my intelligence in the mystery of the Christ,)

and to enlighten all with the knowledge of what is the administration of the mystery hidden throughout the ages in God, who has created all things,

This mystery is great, but I speak as to Christ, and as to the assembly.

and for me in order that utterance may be given to me in the opening of my mouth to make known with boldness the mystery of the glad tidings,