O that thou wouldest rend the heavens This God is said to do, or to bow the heavens, and come down, when he gives a very signal display of his power. It is a metaphor taken from men who, when they would resolutely and effectually help a person in distress, break through every opposition and obstacle. That the mountains might flow down, &c. Or, melt; that all impediments might be removed out of the way. There seems to be an allusion to God's coming down upon mount Sinai in those terrible flames of fire, Judges 5:4-5. As when the melting fire burneth Come with such zeal for thy people that the solid mountains may be no more before thee than metal that runs, or water that boils by the force of a vehement fire; to make thy name That is, thy power; known to thine adversaries That thine enemies, who are also the enemies of thy people, may know thy power, and that thy name may be dreaded among them.
Related Commentaries of Isaiah 64:1
Isaiah 64:1-2
1 Oh that thou wouldest rend the heavens, that thou wouldest come down, that the mountains might flow down at thy presence,
2 As when the meltinga fire burneth, the fire causeth the waters to boil, to make thy name known to thine adversaries, that the nations may tremble at thy presence!