Charles Ellicott Commentary Isaiah 64:2

"as when fire kindleth the brushwood, [and] the fire causeth the waters to boil; to make thy name known to thine adversaries, that the nations may tremble at thy presence!" — Isaiah 64:2 (ASV)

As when the melting fire burneth ... —Better, as when fire Kindleth brushwood, as when fire causeth the water to boil. The two-fold action of material fire is used, as elsewhere, as a symbol of the consuming fire (Hebrews 12:29) of the wrath of Jehovah.