Hebrews 11:11

Genesis 18:11-14 NIV
Abraham and Sarah were already very old, and Sarah was past the age of childbearing. So Sarah laughed to herself as she thought, “After I am worn out and my lord is old, will I now have this pleasure?” Then the Lord said to Abraham, “Why did Sarah laugh and say, ‘Will I really have a child, now that I am old?’ Is anything too hard for the Lord? I will return to you at the appointed time next year, and Sarah will have a son.”

Hebrews 10:23 NIV
Let us hold unswervingly to the hope we profess, for he who promised is faithful.

Romans 4:20-21 NIV
Yet he did not waver through unbelief regarding the promise of God, but was strengthened in his faith and gave glory to God, being fully persuaded that God had power to do what he had promised.