In the literal sense of Sacred Scripture, the “redemption” mentioned in verse 1 probably refers to the temporal redemption of the Jews from their Babylonian captivity, as indicated a little later in verses 3 and 4:
… I give Egypt as your ransom, Ethiopia and Seba in exchange for you. Because you are precious in my eyes, and honored, and I love you, I give men in return for you, peoples in exchange for your life.
Typical of prophecies, the future redemption of the Jews from their Babylonian captivity is so certain that it is spoken of in the past tense, as if it has already taken place.
In the spiritual sense of Sacred Scripture, it probably refers the eternal redemption of mankind won by Christ’s sacrifice on the Cross.