Genesis 21:6

In our father Isaac or the origin is sufficiently expressed, either by grace or by glory: to whom all glory redounds, that he was born to Abraham, a reward for such a worthy and admirable man. Nor is it surprising, since he preceded in the figure of the Lord's generation and passion.

Isaac means "laughter" or "joy." Who is it, then, who begets such a son? It is doubtless he who said of these whom he begot through the gospel: "For you are my joy and crown of glory." For sons of this kind, there is a feast and great joy when they are weaned, for these who "no longer need milk, but strong meat, who by taking up their power have their senses exercised to the discerning of good or evil." There is a great feast for such as these, when they are weaned. But a feast cannot be offered nor joy possessed for those of whom the apostle says, "I gave you milk to drink, not meat; for you were not able as yet, but neither indeed are you able still. And I could not speak to you as to spiritual, but as to carnal, as to little ones in Christ." Let those who wish the divine Scripture to be understood straightforwardly tell us what it means: "I could not speak to you as to spiritual, but as to carnal, as to little ones in Christ; I gave you milk to drink, not meat." Can these words be taken straightforwardly?

Come now, today too, dearly beloved, let us take up the thread of yesterday's remarks and thus set before you this spiritual meal so that we may once more come to learn, as you heard yesterday, the good God's ineffable care and considerateness and the patriarch's remarkable obedience and gratitude. Do you see how the birth of Isaac made Sarah joyful? "She said, 'The Lord brought laughter to me: whoever hears of it will rejoice with me.' " Everyone who hears of it, she is saying, I will convince to be a sharer of my joy. After all, the gift given me by God is wonderful, surpassing human limitations. I mean, who would not be struck, she is saying, to see me feeding and nursing a child in old age after being childless up to this stage of my life? As though surprised and amazed at the event, she added, "Who will let Abraham know that Sarah is nursing a child, that I have borne a son in my old age?" Since what happened was beyond the bounds of nature, she naturally demands, "Who will let him know?" as if to say, Who will imagine it? Who would entertain such an idea? What mind could grasp it? Is there any reasoning that could invent this happening in every detail? Not so remarkable was the incident of the flood of water gushing from the rock in the desert when Moses struck it with his rod as was this instance of a child being born of a womb already deprived of vitality and a ready flow of milk. You see, for the birth to be known to everyone and bring everyone to acceptance of the marvel, for those who heard of it both then and later, she feeds the child and insists on nursing it. She said, "Who will let Abraham know that Sarah is nursing a child, that I have borne a son in my old age," this strange, surprising favor done me in my old age? What is the meaning of "I have borne a son in my old age"?

(2.) When mercies have been long deferred they are the more welcome when they come. (3.) It adds to the comfort of any mercy to have our friends rejoice with us in it: All that hear will laugh with me; for laughing is catching.

And Sarah said, God hath made me to laugh,.... This she said on occasion of the name of her son Isaac, which name her husband had given him by divine direction, and to which she assented.