So it was then, lest the virgin should despair of being able to bear a son, that she received the example of one both old and barren about to bring forth, in order that she might learn that all things are possible with God, even those which seem to be opposed to the order of nature. Whence it follows, For there shall be no word (verbum) impossible with God.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).