When and to whom did God reveal the mystery that had been kept secret?
God kept the mystery, the secret, in His own mind until He revealed it to the Apostle Paul. Paul then wrote so Gentile believers would not be ignorant of it. The Greek word mysterion means secret, and Scripture uses mystery and secret interchangeably.
Les explains that the word Paul uses so often is mysterion in Greek, and it simply means secret. A mystery is a secret, and a secret is a mystery. Paul did not want the Gentile believers to be ignorant of this secret, which God had kept in His own mind until He revealed it to the Apostle Paul. Les stresses that believers are to be well-taught and well-read in the Scriptures, because churches fail when nobody teaches their people what they believe.