The day (h hmera). The day of judgment as in 1 Thessalonians 5:4 (which see), Romans 13:12 ; Hebrews 10:25 . The work (ergon) of each will be made manifest. There is no escape from this final testing. It is revealed in fire (en puri apokaluptetai). Apparently "the day" is the subject of the verb, not the work, not the Lord. See 2 Thessalonians 1:8 ; 2 Thessalonians 2:8 . This metaphor of fire was employed in the O.T. ( Daniel 7:9 ; Malachi 4:1 ) and by John the Baptist ( Matthew 3:12 ; Luke 3:16 ). It is a metaphor that must not be understood as purgatorial, but simple testing (Ellicott) as every fire tests (the fire itself will test, to pur auto dokimasei) the quality of the material used in the building, of what sort it is (opoion estin), qualitative relative pronoun. Men today find, alas, that some of the fireproof buildings are not fireproof when the fire actually comes.