The relative properties must be the divine essence itself. For the relative properties are precisely the subsistent persons. But a person subsisting in the Godhead cannot be something other than the divine essence; and the divine essence is God Himself, as was shown above. Therefore the relative properties are in all reality identical with the divine essence.
Moreover, whatever is in a being besides its essence, is in it accidentally. But there cannot be any accidents in God, as was pointed out above. Accordingly the relative properties are not really distinct from the divine essence.
St. Thomas Aquinas. (1265-1274). Compendium Theologiae: Identity Between the Relative Properties and the Divine Essence, trans. by Cyril Vollert. St. Louis & London: B. Herder Book Co., 1947
All scripture is given by inspiration of God and is profitable for doctrine, reproof, correction, and instruction in righteousness (2 Timothy 3:16).