Jamieson, Fausset and Brown on Daniel 3:17

17. If it be so--Vatablus translates, "Assuredly." English Version agrees better with the original. The sense is, If it be our lot to be cast into the furnace, our God (quoted from De 6:4) is able to deliver us (a reply to Nebuchadnezzar's challenge, "Who is that God that shall deliver you?"); and He will deliver us (either from death, or in death, 2Ti 4:17, 18). He will, we trust, literally deliver us, but certainly He will do so spiritually.