And these three men, Shadrach, Meshach, and Abednego, fell down bound into the midst of the burning fiery furnace.

Wesley's Notes

3:23 Fell down - All this is exprest with emphasis, to make the power of God more glorious in their preservation; for that shame that slew the executioners, might much more easily have killed them, even before they fell down.

Jamieson-Fausset-Brown Bible Commentary

23. fell down-not cast down; for those who brought the three youths to the furnace, perished by the flames themselves, and so could not cast them in. Here follows an addition in the Septuagint, Syrian, Arabic, and Vulgate versions. "The Prayer of Azarias," and "The Song of the Three Holy Children." It is not in the Chaldee. The hymn was sung throughout the whole Church in their liturgies, from the earliest times [Rufinus in Commentary on the Apostles Creed, and Athanasius]. The "astonishment" of Nebuchadnezzar in Da 3:24 is made an argument for its genuineness, as if it explained the cause of his astonishment, namely, "they walked in the midst of the fire praising God, but the angel of the Lord came down into the oven" (vs. 1 and vs. 27 of the Apocryphal addition). But Da 3:25 of English Version explains his astonishment, without need of any addition.

Matthew Henry's Concise Commentary

3:19-27 Let Nebuchadnezzar heat his furnace as hot as he can, a few minutes will finish the torment of those cast into it; but hell-fire tortures, and yet does not kill. Those who worshipped the beast and his image, have no rest, no pause, no moment free from pain, Re 14:10,11. Now was fulfilled in the letter that great promise, Isa 43:2, When thou walkest through the fire, thou shalt not be burned. Leaving it to that God who preserved them in the fire, to bring them out, they walked up and down in the midst, supported and encouraged by the presence of the Son of God. Those who suffer for Christ, have his presence in their sufferings, even in the fiery furnace, and in the valley of the shadow of death. Nebuchadnezzar owns them for servants of the most high God; a God able to deliver them out of his hand. It is our God only is the consuming fire, Heb 12:29. Could we but see into the eternal world, we should behold the persecuted believer safe from the malice of his foes, while they are exposed to the wrath of God, and tormented in unquenchable fires.