What is "v'Revei Di Revi'a'a"?
Rashi: The appearance of the fourth.
How did Nebuchadnetzar know what angels look like?
Rashi: He was with Sancheriv when an angel struck the camp. He was among the 10 survivors. Malbim ? Gavriel, the angel of fire, burned the camp. The angel of hail wanted to cool the furnace to save Chananyah, Misha'el and Azaryah. Gavriel said that it would be a bigger miracle for him to burn outside and cool inside. I.e. the Yesod of lower fire would be Batel in its source above ? fire consumes fire. Every natural power is Batel via its root above. They thought that fire is nature, and must do its action. Now they will know that an intelligent being is appointed over it. The lower fire is Batel to the angel's fire. Outside it will burn those who threw them to the fire, and cool off inside for those who were thrown in. [Gavriel] acts with intellect and choice, unlike natural fire.
