Galatians 4:23
But the one by the bondwoman was born after the flesh; while the one by the freewoman was through the promise.
Hebrews 11:11
Through faith Sarah herself also received power to conceive, even when she was past age, because she accounted him faithful who had promised.
Romans 9:7-8
nor because they are descendants of Abraham are they all children; but, "Thy offspring shall be reckoned from Isaac."
Romans 4:18-21
For he had confident hope in that which was past hope, that he should become a father of many nations, according to that which was spoken, "Thus shall thy offspring be;"
Romans 10:8
But what saith it? "The word is nigh thee, in thy mouth, and in thy heart;" that is, the word concerning faith, which we preach;
Galatians 4:28-29
But ye, brethren, as Isaac was, are children of a promise.