In Parshas Vayeira we open with Avraham asking Sarah to bake some bread for their 3 visitors.
Rashi tells us at 18:8 that while she was kneading the dough, that the course of women returned to her that day. The commentary further elaborates that she had felt her insides churning that menstruation was going to start.

The significance was that Avraham was stringent to keep away from impurity, and would not eat bread made by an impure person.

Note, the bread was for their guests whom he needed to wash their feet for fear that they could be idolatrous arabs.

So I've been puzzled why not yet menstruent impurity stricken this dough would have been a problem to Avraham or to their guests.

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Subsequently, we are told at 18:10-12 that Sarah overheard the visitors report that she would have a child, and she laughed at her insides - in disbelief.

If she was already aware of her insides changing, and changing back to a known capability, I am not sure why this should have been a complete surprise to have disbelief.

Verse 18:11 tells us, apparently going back a bit, that the course of women had ceased. Artscroll uses this past perfect gramatical form eventhough the word is apparently simply past tense in Hebrew.

Verse 18:12 tells us, apparently back to the present tense, that Sarah laughed.

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Subsequently at 21:1 we are told that Hashem remembered Sarah, and Rashi tells us this means with pregnancy. And that this was as a result of Avraham praying for Avimelech and his people.

At 21:6 we are told that Sarah said that Hashem made laughter for her, which Rashi explains to mean that many infertile women were remembered along with Sarah and conceived.

So again we have laughter associated with Sarah having a son, but this time its rejoicing.

But its interesting that the transition toward fertility took several steps, with 1) pre-menstruent churning, 2) disbelieved 1-year fore-knowledge, 3) Avraham's prayer for Avimelech, 4) Hashem remembering Sarah and bringing healing to many infertile women at the same time.


One other loosely related point, back when we first meet Sarah, she is also called Iscah as well. And we are told she was barren.

Somehow Rashi knows that this was certainly a returning of menstruation, not an initial onset. So whatever was the cause of her infertility, it was not a lack of menstruation.

It's not clear from the posuk that Sarah Imenu had begun reexperiencing menstruation at this point. One posuk says: "Chadal l'hyot l'Sarah orach kanashim - the way of women had ceased occuring to Sorah." Had ceased isn't simple past but there really is no past perfect or pluperfect tense in Chumash. You need context. Vehaya, for instance, can mean :"And it was" or "When X will occur then Y will occur." Sorah said: "Acharey bloteey...after my cessation or after my having ceased (balah literally means worn out) shall I have edna (softness) again." It's true that simple pshat contradicts the medrash but you often find medrash contradicting pshat or even other medrashim. It's a good idea to look up someone like the Maharal to get insight into a Medrash.