Isaac is born. Agar and Ismael are cast forth.
“And she conceived and bore a son in her old age, at the time that God had foretold her.” (Genesis 21:2)
The Church which will last until the end of time as promised by Our Lord, in its old age, continues to bring forth fruit despite men’s sins.
“Do you wish to learn the symbolic meaning of Sarah’s sterility? The church was to bring forth the multitude of believers. In order, therefore, that you may not find incredible how one who was childless, fruitless and barren could have given birth, she who by nature was barren went ahead, paving the way for chosen sterility, and Sarah became a type of the church. For just as she gave birth in her old age when she was barren, so too the church, though barren, has given birth for these, the final times.” (4) -St. John Chrysostom
Women's Prayer Group In Christ 