The Unchangeableness of Himself and His Decrees (Observations on the Divine Attributes – Part III) by Jerome Zanchius

Position l. God is essentially unchangeable in Himself. Were He otherwise, He would be confessedly imperfect, since whoever changes must change either for the better or for the worse; whatever alteration any being undergoes, that being must, ipso facto, either become more excellent than it was or lose some of the excellency which it had. [...]