I am the LORD thy God. I Jehovah am thy God (Hebrew. Elohim. App-4). Note the three titles. He was Israel's God by covenant (note the others in the next clause):
the Holy One of Israel, in contrast with all false gods. See note on Isaiah 1:4, and Psalms 71:22.
thy Saviour. This is the third title.
Egypt. Ethiopia and Seba. Egypt. Nubia (Cush), and Ethiopia. These were given to Persia as ransommoney (as it were) for the release of Israel by Persia through the successors of Cyrus. In the time of Isaiah these three were united under one dynasty.
ransom. atonement price. Hebrew. kopher. See note on Exodus 29:33.