The word mystery (mustērion) occurs twenty-seven times in the NT. Twenty of those times, or seventy-four percent, occur in Paul’s writings. It only occurs three times in Matthew, Mark, and Luke. And it occurs four times in Revelation.

We will focus on two things that Paul calls a mystery.

A mystery was not something that had not been revealed in the OT or the preaching of Jesus. It was something that could not be understood without further revelation.

First, Paul says that the Church was a mystery in the OT (cf. Eph 3:9; 6:19). Prior to the birth of the Church, no one knew that Jews and Gentiles would be united in one body; even after the Church’s birth, no one knew that immediately. The early Christians thought that while Samaritans and Gentiles could have everlasting life, they could not be part of the Church. They believed that the Church was just for Jews.

Samaritans were brought into the Church in Acts 8, but that happened only after Peter and John went to Samaria to lay hands on the new believers. The apostles needed to see for themselves that God intended the Samaritans to become part of the Church.

Gentiles were brought into the Church in Acts 10. Again, Peter was present. He was the one who led them to faith in Christ (Acts 10:43-48; 11:14; 15:7-11).

The OT did talk about Gentiles being in the kingdom. Some believe that the Church was even discussed in the OT. I heard Zane Hodges give a great message on Psalm 45. He thought that the bride in that Psalm was the Church, but this could not be known until the NT. He thought that “the king’s daughters” referred to Israel.

Many believe there are types of the Rapture of the Church in the OT as well (e.g., Eve being brought to Adam in Genesis 2, Enoch being taken alive into heaven in Genesis 5, Lot and his family being taken out of Sodom before its destruction, in Genesis 19, and possibly Noah and his family being delivered from the worldwide destruction in Genesis 6-9). Yet the church and the rapture of the church were mysteries before the NT was written.

The “mystery of the gospel” (Eph 6:19) is the mystery of the good news that Jews and Gentiles are united in the Church. Paul said in Eph 3:2-6 that God “made known to me the mystery…that the Gentiles should be fellow heirs, of the same body, and partakers of the promise of Christ through the gospel.”

Paul meant the same thing when he spoke of “the mystery of Christ” (Eph 3:4; Col 4:3; 1 Tim 3:16). It was the mystery of Jews and Gentiles on equal footing a new body, the Church. See here and here for articles on “the mystery of Christ.”

Christianity is not a “mystery religion.” We do not have secret elaborate initiation rituals. We do not have special knowledge that is hidden except to those in the upper echelons of our ranks. The mystery religions that grew up in the first three centuries mimicked the Christian faith. Gotquestions.org writes, “…a number of historians and scholars have argued that Christianity borrowed from the mystery religions or that the mystery religions influenced Christianity; however, a strong case can be made that the opposite is true—that the mystery religions borrowed from Christianity to add to their mythologies. Besides, the similarities between Christianity and the mystery religions are merely superficial” (see here).

The next time you see the word mystery in Paul’s writing or other NT passages, think of the Church, Jews and Gentiles united in one body. The Church was a mystery in the OT. We required more revelation to understand that Gentiles would be “fellow heirs of the same body.”