God is good since He is God, and therefore good by Himself and from Himself, not by another’s work.

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God made everything good, but none other has made Him good. Since His goodness was not received from another, He is good by His own nature. He could not receive goodness from the things He created since they were created after Him. His creatures received all of their beings and attributes from Him, and so they can bestow no blessing or gift on Him. No other God preceded Him in whose inheritance and treasures of goodness He might be a successor: God is absolutely His own goodness. He needed none to make Him good, but all things need Him in order to be good. Creatures are good because He made them so and they imitated His nature. He is good without clinging to any goodness outside of Himself.

Goodness is not a quality nor a habit added to God’s essence, but is instead a nature. Goodness is itself the essence of God.

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From the book “Boundlessly Good”