CATECHISM OF THE CATHOLIC CHURCH
SECOND EDITION

Paragraphs 227–231

227 It means trusting God in every circumstance, even in adversity. A prayer of St. Teresa of Jesus wonderfully expresses this trust:

Let nothing trouble you / Let nothing frighten you
Everything passes / God never changes
Patience / Obtains all
Whoever has God / Wants for nothing
God alone is enough.

228 "Hear, O Israel, the LORD our God is one LORD..." (Dt 6:4; Mk 12:29). "The supreme being must be unique, without equal. . . If God is not one, he is not God" (Tertullian, Adv. Marc., 1, 3, 5: PL 2, 274).
229 Faith in God leads us to turn to him alone as our first origin and our ultimate goal, and neither to prefer anything to him nor to substitute anything for him.
230 Even when he reveals himself, God remains a mystery beyond words: "If you understood him, it would not be God" (St. Augustine, Sermo 52, 6, 16: PL 38, 360 and Sermo 117, 3, 5: PL 38, 663).
231 The God of our faith has revealed himself as HE WHO IS; and he has made himself known as "abounding in steadfast love and faithfulness" (Ex 34:6). God's very being is Truth and Love.