Albert Barnes Commentary Isaiah 45:4

"For Jacob my servant`s sake, and Israel my chosen, I have called thee by thy name: I have surnamed thee, though thou hast not known me." — Isaiah 45:4 (ASV)

For Jacob my servant’s sake - (see the note at Isaiah 42:19). The statement here is that God had raised up Cyrus on account of his own people. The sentiment is common in the Bible that kings and nations are in the hand of God; and that he overrules and directs their actions for the accomplishment of his own purposes, and especially to protect, defend, and deliver his people (see the note at Isaiah 10:5).

I have surnamed you - On the meaning of the word ‘surname,’ see the notes at Isaiah 44:5. The reference here is to the fact that he had appointed him to accomplish important purposes, and had designated him as his ‘shepherd’ (Isaiah 44:28), and his ‘anointed’ (Isaiah 45:1).

Though you have not known me - Before he was called to accomplish these important services, he was a stranger to Yahweh. It was only when he would be so signally favored by heaven, and would be made acquainted with the divine will in regard to the deliverance of his people and the rebuilding of the temple (Ezra 1:1–3), that he would become acquainted with the true God.