Revelation 10:7

but in the days of the voice of the seventh angel, when he is about to sound, then the mystery of God is finished, as He preached to His servants the prophets.

Romans 16:25

Now to Him who is able to establish you according to my gospel and the preaching of Jesus Christ, according to the revelation of the mystery which has been kept secret for long ages past,

Amos 3:7

Surely the Lord God does nothing
Unless He reveals His secret counsel
To His servants the prophets.

Luke 24:44-47

Now He said to them, These are My words which I spoke to you while I was still with you, that all things which are written about Me in the Law of Moses and the Prophets and the Psalms must be fulfilled.”

Acts 3:21

whom heaven must receive until the period of restoration of all things about which God spoke by the mouth of His holy prophets from ancient time.

Romans 11:25

For I do not want you, brethren, to be uninformed of this mystery—so that you will not be wise in your own estimation—that a partial hardening has happened to Israel until the fullness of the Gentiles has come in;

Ephesians 3:3-9

that by revelation there was made known to me the mystery, as I wrote before in brief.

Revelation 11:15-18

Then the seventh angel sounded; and there were loud voices in heaven, saying,The kingdom of the world has become the kingdom of our Lord and of His Christ; and He will reign forever and ever.”

Treasury of Scripture Knowledge

Summary

But in the days of the voice of the seventh angel, when he shall begin to sound, the mystery of God should be finished, as he hath declared to his servants the prophets.

Bible References

In the

Revelation 11:15
Then the seventh angel sounded; and there were loud voices in heaven, saying,The kingdom of the world has become the kingdom of our Lord and of His Christ; and He will reign forever and ever.”

The mystery

Romans 11:25
For I do not want you, brethren, to be uninformed of this mystery—so that you will not be wise in your own estimation—that a partial hardening has happened to Israel until the fullness of the Gentiles has come in;
Romans 16:25
Now to Him who is able to establish you according to my gospel and the preaching of Jesus Christ, according to the revelation of the mystery which has been kept secret for long ages past,
Ephesians 3:3
that by revelation there was made known to me the mystery, as I wrote before in brief.

As he

Luke 24:44
Now He said to them, These are My words which I spoke to you while I was still with you, that all things which are written about Me in the Law of Moses and the Prophets and the Psalms must be fulfilled.”
Acts 3:21
whom heaven must receive until the period of restoration of all things about which God spoke by the mouth of His holy prophets from ancient time.