Mark 4:11
And he said unto them,
Unto you it is given to know the mystery of the kingdom of God: but unto them that are without, all these things are done in parables:
Romans 16:24-26
24 The grace of our Lord Jesus Christ be with you all. Amen.
25 Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ,
according to the revelation of the mystery, which was kept secret since the world began,
26 But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith:
1 Corinthians 2:7
But
we speak the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory:
Ephesians 1:9
Having made known unto us the mystery of his will, according to his good pleasure which he hath purposed in himself:
Ephesians 3:4
Whereby, when ye read,
ye may understand my knowledge in the mystery of Christ)
Ephesians 3:9
And
to make all men see what is the fellowship of the mystery, which from the beginning of the world hath been hid in God, who created all things by Jesus Christ:
Colossians 1:26
Even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints:
John 15:15
Henceforth I call you not servants; for the servant knoweth not what his lord doeth: but I have called you friends; for
all things that I have heard of my Father I have made known unto you.
1 John 2:20-21
20 But ye have an unction from the Holy One, and
ye know all things.
I have not written unto you because ye know not the truth, but because ye know it, and that no lie is of the truth.
1 John 2:27
But
the anointing which ye have received of him abideth in you, and ye need not that any man teach you: but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as it hath taught you, ye shall abide in him.
The NT use of the word mystery (G3466 μυστήριον musterion) is that of a secret once hidden but now revealed unto us by the Holy Spirit. Paul did not say we "speak in a mystery," he said "we speak the wisdom of God." We cannot speak what we do not understand. That is why the Holy Spirit was given, to guide us into all truth. We "need not that any man teach" us, the anointing of the Holy Spirit teaches us of ALL things.
There is nothing hidden from the child of God. All things are revealed to us by His Spirit through the Scriptures.