"God is not human, that he should lie, not a human being, that he should change his mind. Does he speak and then not act? Does he promise and not fulfil?" (Numbers 23:19)
Balak takes Balaam to a high place to see the Israelite camp. Balaam gives his first oracle: how can I curse those whom God has not cursed? From the rocky peaks I see them, from the heights I view them. I see a people who live apart and do not consider themselves one of the nations. Who can count the dust of Jacob or number even a fourth of Israel? Let me die the death of the righteous and may my end be like theirs. Balak is furious: I brought you to curse my enemies but you have blessed them instead. Balaam answers: must I not speak what the LORD puts in my mouth?
Balak tries a different vantage point. Balaam gives his second oracle, containing the great statement of divine faithfulness: God is not human, that he should lie, not a human being, that he should change his mind. Does he speak and then not act? Does he promise and not fulfil? He has received a command to bless; he has blessed and cannot change it. Behold, I have received a command to bless; he has blessed and I cannot change it. The Catechism identifies this as one of the clearest Old Testament statements of the divine truthfulness: God's word, once spoken, is efficacious and irrevocable (CCC 215). The attempt to curse what God has blessed is futile, because the word of God does not return void.
Brothers and sisters, God is not human, that he should lie. Every promise God has made to you is still in force. He has not changed his mind about the covenant. He does not revise the blessings he has pronounced. The word that went out will accomplish what it was sent to do. Hold every promise he has made to you with that certainty.
Lord God, you do not lie, you do not change your mind, you do not speak without acting or promise without fulfilling. We take you at your word. Every promise you have made, we hold. Every blessing you have spoken, we receive. Through Christ our Lord. Amen.