He answered and said, Lo, I see four men loose, walking in the midst of the fire, and they have no hurt; and the form of the fourth is like the Son of God.
Lo, I see four men - "four," whereas but three had been cast in.
Loose - whereas they had been cast in "bound." Nebuchadnezzar's question in Daniel 3:24 is as if he can scarcely trust his own memory as to a fact so recent, now that he sees, through an aperture in the furnace, what seems to contradict it.
Walking in the midst of the fire - image of the godly unhurt and at large (John 8:36). "Though I walk in the midst of trouble, thou wilt revive me" (Psalms 138:7: cf. Psalms 23:3-4; and especially Isaiah 43:1-2, "Fear not: for I have redeemed thee, I have called thee by thy name; thou art mine ... when thou walkest through the fire, thou shalt not be burned; neither shall the flame kindle upon thee"). They walked up and down in the fire, not leaving it, but waiting for God's time to bring them out, just as Jesus waited in the tomb, as God's prisoner, until God should let Him out (Acts 2:26-27). So Paul (2 Corinthians 12:8-9). So Noah waited in the ark, after the flood, until God brought him forth (Genesis 8:12-18).
The form of the fourth is like the Son of God. Unconsciously, like Saul, Caiaphas (John 11:49-52), and Pilate, he is made to utter divine truths, the full import of which he did not himself understand. "Son of God" in his mouth means only an "angel" from heaven, as Daniel 3:28 proves, "Blessed be the God of Shadrach, etc., who hath sent his angel." (Compare Job 1:6; Job 38:7, where "the sons of God" mean the angels; Psalms 34:7-8, "The angel of the Lord encampeth round about them that fear him, and delivereth them;" and the probably pagan centurion's exclamation, Matthew 27:54, "Truly this was the Son of God"). The Chaldeans believed in families of gods: Bel, the supreme god, accompanied by the goddess Mylitta, being the father of the gods: thus by the expression he meant one sprung from and sent by the gods. Really it was the "messenger of the covenant," who herein gave a prelude to His incarnation.