In God "there is no variation or shadow due to change." 26 God is "HE WHO IS", from everlasting to everlasting, and as such remains ever faithful to himself and to his promises.
Catechism number 215
"The sum of your word is truth; and every one of your righteous ordinances endures forever."30 "and now, O LORD God, you are God, and your words are true";31 this is why God's promises always come true.32 God is Truth itself, whose words cannot deceive. This is why one can abandon oneself in full trust to the truth and faithfulness of his word in all things. the beginning of sin and of man's fall was due to a lie of the tempter who induced doubt of God's word, kindness and faithfulness.