That which is secret, hidden, or beyond normal human understanding, although it may be revealed or disclosed to certain people. God’s knowledge was a “mystery” because some of it was not known, and even when known, was not always understood. God delivered it in person (Gen 17:1), through an angel (from heaven, Gen 22:11), through dreams (Gen 20:3), or through the “Spirit of the Lord” (2Sam 23:2). In the NT, God is said to have kept the divine mystery hidden for ages, while revealing it to the ancient prophets and the Christian apostles (Rom 16:25-26; 1Cor 2:7; 1Cor 4:1; Eph 3:9; Heb 1:1-2; 1Pet 1:10-12; Rev 10:7). Often the mystery was the heart of the Christian gospel under various names: “God’s mystery” (Col 2:2; Rev 10:7); “mystery of his will” (Eph 1:9); “mystery of Christ” (Eph 3:4; Col 4:3); “mystery of the gospel” (Eph 6:19); “mystery of the faith” (1Tim 3:9); “mystery of our religion” (1Tim 3:16). (Mark 4:11-12) tries to explain why so few people understand “the secret [lit., mystery] of the kingdom of God.” Paul explained the nonbelief of Jews as “a mystery”: God has hardened part of Israel “until the full number of the Gentiles has come in” (Rom 11:25-26). Other Christian problems too were treated as mysteries: the nature of the general resurrection (1Cor 15:51-55); the time of Jesus’s return and the disbelief of many (2Thess 2:1-12); the question of whether salvation is also intended for Gentiles (Eph 3:4-6; Col 1:25-27). The meaning of a passage in the OT can be a mystery, as in (Gen 2:24 and Eph 5:31-32). Speaking in tongues is uttering “mysteries in the Spirit” (1Cor 14:2).
