John Calvin Reformed @genevareformer

5. I am Jehovah. He confirms the preceding statement, and the repetition is not superfluous; for it was proper that it should be often repeated to Cyrus, that there is one God, by whose hands all rulers and nations are governed, that he might be drawn aside from all delusions and be converted to the God of Israel.

Matthew Henry Presbyterian @wholebiblehenry

God here asserts his sole and sovereign dominion, as that which he designed to prove and manifest to the world in all the great things he did for Cyrus and by him. Observe, I. How this doctrine is here laid down concerning the sovereignty of the great Jehovah, in two things: - 1. That he is God alone, and there is no God besides him.

Commenting on Isaiah 45:5-10

John Gill Reformed Baptist @doctorgill

I am the Lord, and there is none else,.... Whom thou, O Cyrus, for the words are directed to him, ought to own, serve, and worship: there is no God besides me; in heaven or earth, in any of the countries conquered by thee, and thou rulest over; for though there were gods and lords many, so called, these were only nominal fictitious deities; not...