By faith, even though Sarah herself was barren and he was too old, he received the ability to procreate, because he regarded the one who had given the promise to be trustworthy.
The woman did conceive, and at the specified time the next year she gave birth to a son, just as Elisha had told her.
“And look, your relative Elizabeth has also become pregnant with a son in her old age – although she was called barren, she is now in her sixth month!
This means it is not the children of the flesh who are the children of God; rather, the children of promise are counted as descendants.
But one, the son by the slave woman, was born by natural descent, while the other, the son by the free woman, was born through the promise.
And let us hold unwaveringly to the hope that we confess, for the one who made the promise is trustworthy.