When thou didst terrible things... — The latter clause, “thou camest down ...” is supposed by some critics to be an accidental repetition from Isaiah 64:1. By others it is taken as an intentional repetition, emphasising the previous assertion, after the manner of Hebrew poetry. The latter view seems to have most in its favour.
Related Commentaries of Isaiah 64:3
Isaiah 64:3
3 When thou didst terrible things which we looked not for, thou camest down, the mountains flowed down at thy presence.