The term “mystery” refers in Scripture to intentions God had from the beginning, but he had not fully revealed the content of those intentions from the beginning. The reference in Genesis 3:15 to the head of the seed of the woman crushing the head of the seed of the serpent forms an example. It is not till centuries later, with further revelation from the Lord God, that the “mystery” hinted at in Genesis 3:15 becomes clear to Bible readers. Through his prophets in the Old Testament, the Lord God had revealed more intentions, the significance of which did not become evident till years had passed (see Ephesians 3:4–6). Now, with the promise that there would be “no more delay,” this angel declares that “the mystery of God would be fulfilled.”
7 but that in the days of the trumpet call to be sounded by the seventh angel, the mystery of God would be fulfilled, just as he announced to his servants the prophets.