What was the relationship between Sarah and Mary?
The Church teaches that Mary’s mission was prepared by holy women, like Sarah, who conceived in her old age. Genesis 18:14; Luke 1:37
What the Bible says
Genesis 18:14
Is there any thing hard to God? According to appointment I will return to thee at this same time, life accompanying, and Sara shall have a son.
Luke 1:37
Because no word shall be impossible with God.
Douay-Rheims Bible (Challoner revision), public domain.
What the Church teaches
Against all human expectation, God chooses what seemed weak to show that he is faithful to his promise.
Catechism 489 · Catechism of the Catholic Church