When Sarah was told about having a child at such an old age, she laughed in disbelief. Let us cite the pesukim: ואברהם ושרה זקנים באים בימים חדל להיות לשרה ארח כנשים... אחרי בלותי היתה לי עדנה ואדני זקן... היפלא מה' דבר למועד אשוב אליך..., Avraham and Sarah were old, well on in years, the manner of women had ceased to be with Sarah. Sarah laughed saying after I had withered shall I again have delicate skin? And my husband is old. Then Hashem said to Avraham why is it that Sarah laughed saying shall I in truth bear a child although I have aged. Is anything beyond Hashem?! At the appointed time I will return to you at this time next year, and Sarah will have a son.
The Meor V’shemesh (1751-1823) struggles to understand where Sarah’s Emuna was. Didn’t she know that Hashem could give her children at an old age?
The Meor V’shemesh understands this episode in a different light. Through the act of relations of a couple, the physical body of a child can be born. However, Avraham and Sarah purified their bodies so much and had no physicality to their act of relations since it was with such holiness and purity.
In this light we can grasp the meaning of the pesukim. ואברהם ושרה זקנים באים בימים: זקן, the Gemara says, refers to wisdom. This means they cleansed themselves spiritually more and more as they got older. The next words are חדל להיות לשרה ארח כנשים: she wasn’t naturally physical like other women. She therefore said אחרי בלותי from the term בלתי meaning I myself that has no physicality. היתה לי עדנה: I can’t bring myself to any physicality which is under the domain of time as עדנה can mean time as in עדן. ואדני זקן: my master Avraham clings to Hashem so much (as זקן is a contraction of זה שקנה חכמה, one who has acquired wisdom) and he also has no physicality to him. Since in order to bring about a child into the world there must be some physicality involved in the act of relations, how is it then possible, Sarah wondered, for her to have a child!
Hashem answered her היפלא מה' דבר למועד אשוב אליך. מועד refers to time. So Hashem answered, אשוב אליך, I can return you under the domain of time, in order that you can have some physicality so that you can bear a child — ולשרה בן.
