For Zion's sake will I not hold my peace, and for Jerusalem's sake I will not rest, until the righteousness thereof go forth as brightness, and the salvation thereof as a lamp that burneth.
For Zion's sake will I not hold my peace. "I" - the prophet, as representative of all the praying people of God who love and intercede for Zion (cf. Isaiah 62:6-7; Psalms 102:13-17); or else Messiah, the great Intercessor (cf. Isaiah 62:6). So Messiah is represented as unfainting in His efforts for His people (Isaiah 42:4; Isaiah 50:7).
Until the righteousness thereof go forth as brightness - not its own righteousness inherently, but imputed to it for its restoration to God's favour: hence, "salvation" corresponds to it in the parallelism. "Judah" is to be 'saved' through "the Lord our (Judah's and the Church's) righteousness" (Jeremiah 23:6).
As brightness ( kanogah (H5051)) - properly the bright shining of the rising sun (Isaiah 60:19; Isaiah 4:5; 2 Samuel 23:4; Proverbs 4:18). And the salvation thereof as a lamp (that) burneth - blazing torch.