Why did Avraham Have to Give a Recipe to Sarah?

Question

When the 3 visitors show up, Avraham indicates he will get them bread. He then runs off and tells his wife not just what to make but what recipe to use (Gen 18,6):

"וַיְמַהֵר אַבְרָהָם הָאֹהֱלָה אֶל־שָׂרָה וַיֹּאמֶר מַהֲרִי שְׁלֹשׁ סְאִים קֶמַח סֹלֶת לוּשִׁי וַעֲשִׂי עֻגוֹת׃ "

Abraham hastened into the tent to Sarah, and said, “Quick, three seahs of choice flour! Knead and make cakes!”

Did she not know how to make bread? Would she normally use a non-flour product or the wrong amount? He says "asi ugot" (make cakes) but he doesn't trust her to know how? Couldn't he just have told her to make food (in general or in specific) and let her collect the ingredients?

The commentators discuss why "cakes" (for speed's sake) and why he tells her to knead the bread (to avoid it's turning into chametz) but I haven't seen anyone discuss why he needed to tell her the amount, or, more precisely, why he assumed she wouldn't know the right amount.

Answer 1

Being that you provided answers for the preparation of cakes and kneading, I will try to answer why he told her to make three Se'ah of flour:

(Mefarshim here)

Your question is valid according to most mefarshim, who say that she was supposed to take only the purest flour from these three se'ah (1/3 of an Ephah, a tremendous amount), until it would reach a more reasonable (smaller amount). According to them, we would have to say that he was specifying such a large amount so she would know how pure the flour should be.

However, Shadal suggests on a Peshat level that the loaves were very large so they could take the bread with them. If so, he needed to specify how large they should be.

Similarly, Radak says that he told her to bake three Se'ah-sized loafs, one for each guest. That is because it was in an honorable fashion, but much more than would regularly be required for three guests. See also Rabbeinu Bachya/Bechayei, who expand(s) on this theme of 'three for honor'.