# The mystery was made known to me by revelation

This can be stated in active form. Alternate translation: "I learned about the mystery by revelation" or "God revealed the mystery to me" (See: [[rc://en/ta/man/jit/figs-activepassive]])

# The mystery

The mystery is God's plan, which God had not clearly told people about earlier. Alternate translation: "God's secret plan" or "The hidden truth"

# as I have written briefly

Paul refers to another letter he had written to these people.