John Mayer on Daniel 3:24-25

Shadrach, Meshach and Abednego, the most valiant champions of God, cast into the extremely hot fiery furnace, were seen walking in the furnace with a fourth man being among them like the Son of God… This appearance was certainly a prelude of his future incarnation and after that of his continued presence with his people to the end of the world; a presence especially seen in their sufferings, as he showed himself to Stephen before he was to be stoned. Thus it is understood by Tertullian, who says Christ appeared to the king of Babylon in the fiery furnace; the fourth with his martyrs as the Son of God.

Ezekiel, Daniel, ed. Carl L. Beckwith, Reformation Commentary on Scripture, OT Vol. XII, p. 275.