en_tn/1co/03/13.md

his work will be revealed

This can be stated in active form. Alternate translation: "God will show everyone what the builder has done" (See: rc://en/ta/man/jit/figs-activepassive)

for the day will reveal it

The "day" refers to the time when God will judge everyone. When God shows everyone what these teachers have done, it will be like the sun has come up to reveal what happened during the night. (See: rc://en/ta/man/jit/figs-metaphor)

For it will be revealed in fire. The fire will test the quality of what each one has done

Just as fire will reveal the strengths or destroy the weaknesses of a building, God's fire will judge man's efforts and activities. Alternate translation: "God will use fire to show the quality of his work" (See: rc://en/ta/man/jit/figs-metaphor)