Faith is not built on probability, but on His power.

1 When Abram was ninety-nine years old, the Lord appeared to him and said, “I am God Almighty; walk before me faithfully and be blameless. 2 Then I will make my covenant between me and you and will greatly increase your numbers.” 3 Abram fell facedown, and God said to him, 4 “As for me, this is my covenant with you: You will be the father of many nations.
Genesis: 17:1-4

God reclaims and transforms identity.

5 No longer will you be called Abram; your name will be Abraham, for I have made you a father of many nations. 6 I will make you very fruitful; I will make nations of you, and kings will come from you. 7 I will establish my covenant as an everlasting covenant between me and you and your descendants after you for the generations to come, to be your God and the God of your descendants after you. 8 The whole land of Canaan, where you now reside as a foreigner, I will give as an everlasting possession to you and your descendants after you; and I will be their God.
Genesis 17:5-8

15 God also said to Abraham, “As for Sarai your wife, you are no longer to call her Sarai; her name will be Sarah. 16 I will bless her and will surely give you a son by her. I will bless her so that she will be the mother of nations; kings of peoples will come from her.”
Genesis 17:15-16

When God seals it, no one can steal it!

19 Then God said, “Yes, but your wife Sarah will bear you a son, and you will call him Isaac. I will establish my covenant with him as an everlasting covenant for his descendants after him. 20 And as for Ishmael, I have heard you: I will surely bless him; I will make him fruitful and will greatly increase his numbers. He will be the father of twelve rulers, and I will make him into a great nation. 21 But my covenant I will establish with Isaac, whom Sarah will bear to you by
this time next year.”
Genesis 17:19-21

He has also put his seal on us and given us his Spirit in our hearts as a guarantee.
2 Corinthians 1:22