Isaiah 43:3

For I am the Lord thy God, the Holy One of Israel, thy Saviour,
&c.] The Lord is the covenant God of his people, holy in himself, and the sanctifier of them, and their Saviour in time of trouble; and therefore need no doubt of his presence and support amidst all their afflictions; and besides they should call to mind past experiences of his goodness, to encourage their faith in him, as to present help and assistance: I gave Egypt for thy ransom;
he sacrificed the Egyptians instead of the Israelites; he destroyed the firstborn of Egypt, and saved Israel his firstborn; he drowned the Egyptians in the Red sea, when the Israelites passed safely through it; and the destruction of the former was to make way for the salvation of the latter, and so said to be a ransom for them; see ( Proverbs 11:8 ) ( 21:18 ) : Ethiopia and Seba for thee;
this refers either to the rumour brought to Sennacherib of Tirhakah king of Ethiopia coming against him to war, which diverted him from the siege of Jerusalem for a time, and caused him to turn his forces upon the Ethiopians and Sabeans, whereby the Jews had a respite, ( 2 Kings 19:9 ) or rather to the overthrow of the Ethiopians in the time of Asa, ( 2 Chronicles 14:9-13 ) or to the king of Assyria, perhaps Shalmaneser's being diverted from Palestine and Judea, and turning his forces upon Egypt and Ethiopia, as in ( Isaiah 20:1 ) and the Lord, by putting his people in mind of these instances, suggests hereby that he will sacrifice all their enemies, rather than they shall be destroyed, and therefore they need not fear.