What does Aquinas say about God's action and essence in the book, Introduction to Saint Thomas Aquinas?

Aquinas asserts that God's action and essence are in constant unity. In so being, God's power dwells throughout every one of God's actions. Readers can understand this. Whenever you act in accordance with your own truth and values, then your behavior is in unity with your essence. When you behave in a way that does not express the truth, you are 'acting' and that your behavior and essence are not united at that moment.