Why no 'famous' derasha on Isha Ki Tazria?

Summary: Maybe there is. Regardless, what about the law of conservation of derashot?

Post: Parashat Tazria leads off with the following:

2. Speak to the children of Israel, saying: If a woman conceives and gives birth to a male, she shall be unclean for seven days; as [in] the days of her menstrual flow, she shall be unclean.		ב. דַּבֵּר אֶל בְּנֵי יִשְׂרָאֵל לֵאמֹר אִשָּׁה כִּי תַזְרִיעַ וְיָלְדָה זָכָר וְטָמְאָה שִׁבְעַת יָמִים כִּימֵי נִדַּת דְּוֹתָהּ תִּטְמָא:
When a woman conceives. R. Simlai said: Just as the creation of mankind [came only] after [that of] every animal, beast and bird in the Work of Creation, so too his teaching is explained [only] after the teaching [regarding] animals, beasts and birds.		אשה כי תזריע: אמר ר' שמלאי כשם שיצירתו של אדם אחר כל בהמה חיה ועוף במעשה בראשית, כך תורתו נתפרשה אחר תורת בהמה חיה ועוף:
When.... [she] conceives. [This comes] to include even [when the embryo] is born mushy--- [that is, as though] it was crushed and became as semen--- its mother [is ritually] unclean as if it were childbirth.		כי תזריע: לרבות שאפילו ילדתו מחוי, שנמחה ונעשה כעין זרע, אמו טמאה לידה:

Yet, there is a 'famous' derasha which is missing here -- that if a woman gives forth seed first -- אִשָּׁה כִּי תַזְרִיעַ -- then, she will give birth to male offspring -- וְיָלְדָה זָכָר.

We see this, e.g., in Midrash Tanchuma:

דבר אחר:
אשה כי תזריע 

אם קדמה האשה, יולדת זכר.
קדם האיש, יולדת נקבה. 

Perhaps we would find it surprising that this derasha is not brought forth by Rashi.

I did actually find this derasha in an early ktav yad of Rashi, Munich, from 1233:

The second red underline is the famous derasha, that if the woman is מזרעת first, then she has a male child, while if the man is mazria first, then she will have a female child. The third red underline is the Rashi above.

Of course, this particular manuscript often seems to have insertions from other sources, expanding upon Rashi. So even though it is stated as davar acher, this does not mean that Rashi necessarily said both. But, if he did, then it cuts the question off at its source.

At any rate, this is a question asked by various meforshei Rashi. Well, not precisely this question. It is more that there is a law of conservation of derashot, that if there is an extraneous word or phrase, then it can be used for one and one derasha only. You cannot derive two things from the same phrase. If so, the derasha that Rashi gives above would cut off any other derasha on this basis. And yet, Rashi elsewhere subscribes to this derasha!

Thus, we have the following in the Taz:

כי תזריע ... ונעשה כעין זרע  -- this is based on that it is written ki tazria, which is extraneous {for how else could she give birth?!}. And it is difficult, for behold we need it for another derasha, in perek Hamapelet, which Rashi brings in parashat Vayigash, on the following pasuk {Bereishit 46:15}: אֵלֶּה בְּנֵי לֵאָה אֲשֶׁר יָלְדָה לְיַעֲקֹב בְּפַדַּן אֲרָם וְאֵת דִּינָה בִתּוֹ כָּל נֶפֶשׁ בָּנָיו וּבְנוֹתָיו שְׁלֹשִׁים וְשָׁלֹשׁ, ' These are the sons of Leah, that she bore to Jacob in Padan Aram, and Dinah his daughter. All the souls of his sons and daughters were thirty three,' where Rashi writes, אלה בני לאה. ואת דינה בתו: הזכרים תלה בלאה והנקבות תלה ביעקב, ללמדך אשה מזרעת תחלה יולדת זכר, איש מזריע תחלה יולדת נקבה, the males it attributes to Leah and the females are attributed to Yaakov, to teach you that when a woman gives forth seed first, she will give birth to a male, while if a man gives forth seed first, she will give birth to a female.


And Rabbi Eliyahu Mizrachi wrote that it makes sense that the derasha above is based on that it stated ki tazria and not im tazria, which would indicate a language of doubt, while ki implies certainty, and this is so {a certainty} if she gives forth seed first. {Thus, the derasha of ונעשה כעין זרע is on the entirety of the extraneous phrase, while the other derasha


And a question on this is that behold, ki appears in place of im in many places, such as Nefesh ki takriv and, like it, Ki Teitzei lamilchama. And it appears to me that there is a resolution to this, that if it is for the derasha here, that even if she bore something akin to seed, there is a difficulty regarding this, for how could it continue וְיָלְדָה זָכָר, which implies that the law of that which comes from כִּי תַזְרִיעַ, which is that which looks like seed, has the law akin to that which is mentioned after it, which is וְיָלְדָה זָכָר, in terms of the ritual impurity associated with childbirth. And this just isn't so! For if she bears something akin to seed, it is a safek, a doubt, and it is necessary for her to have upon herself the law of {bearing} a female, stringently. Rather, perforce, this is what it means to say: A woman, when she gives forth seed first, certainly she will give birth to a male. And one cannot say that perhaps this is the only thing this comes to teach, for upon this we can ask what relationship this teaching, of giving forth seed first, has to the law of ritual impurity of childbirth, which is, after all, the subject of this parasha. Rather, perforce, this is informing us that there is a nafka mina, a practical halachic distinction, which applies to the ritual impurity of childbirth, and we say regarding it, because of safek, that we act stringently."

This ends the Taz.

I would analyze this is a far different way. First, what are Rashi's sources? Looking at Mekorei Rashi, the very first Rashi on the sidra is from Vayikra Rabba, as we might intuit from its style -- its purpose is to explain the placement of this parasha in the grander scheme of things. But then our Rashi, about לרבות שאפילו ילדתו מחוי, has the characteristics of midrash aggadah. And it, and subsequent Rashis, are indeed drawn from the gemara in Niddah or from the Sifra. In this case, the Sifra has something similar, on the word tazria, but not precisely the same. Niddah 27b has:

א"ר אמי אמר רבי יוחנן ומודה רבי שמעון שאמו טמאה לידה אמר ההוא סבא לרבי אמי אסברא לך טעמא דרבי יוחנן דאמר קרא (ויקרא יב, ב) אשה כי תזריע וילדה זכר וגו' אפילו לא ילדה אלא כעין שהזריעה טמאה לידה

Or in English:

R. Ammi citing R. Johanan stated: R. Simeon, however,⁵³  agrees that its mother is unclean by reason of childbirth. Said a certain old man to R. Ammi: 'I will explain to you R. Johanan's reason:⁵⁴  For Scripture says, If a woman conceived seed⁵⁵  and bore a man-child etc.,⁵⁶  which implies: Even if she bore in the same manner only as she 'conceived seed'⁵⁷  she is unclean by reason of childbirth.

And Rashi there explains the derasha as:

כעין שהזריעה - כלומר דנימוח כזרע:

Rashi's purpose through Tazria is to bring us much of the relevant midrash halacha on this sidra so that we can understand how Chazal interpreted it. He does not bring every midrash halacha, but a cursory examination of what Rashi does say reveals that this is his agenda.

I can understand why Rashi would not bring the midrash about the woman giving forth seed first and thus having a male child. This is not a midrash halacha, and would be a digression and distraction from his purpose.

What about the law of conservation of derash, that only one derasha  may come from every extraneous word or phrase? I would answer this in one of several different ways:

1) This is not such a strict rule when we are dealing with midrash aggada, or better, when one derasha is in the realm of midrash halacha and the other is in the realm of midrash aggadah. These are different spheres.

2) Even without this, the derasha of ki tazria, as we understand it from the gemara in Niddah, is that we are inclusive of even the zeria, or rather, something that looks like just zera. A typical ribbuy, in other words. In contrast, the idea of giving seed first to produce a male child is derived from the opportune juxtaposition, forming the statement אִשָּׁה כִּי תַזְרִיעַ וְיָלְדָה זָכָר, as a cause and effect. As with many such derashot, this opportune juxtaposition forms a statement completely independent of the normal context -- hyper-literalism or significance-maximalism is what some scholars call this. These are different features being darshened.

3) This principle of giving seed first is a known fact, that the gender characteristics of the later seed obliterate the gender characteristics of the earlier seed (though one we now know to be false). As such, it might just be a convenient asmachta to something known anyway. Elsewhere, Chazal give derashot to prove that the sun rises in the east and sets in the west! Is this necessary? Of course not. So too here, this might just be a remez, to show how these scientific facts are hinted to in the Torah, and such a derasha would not gobble up the relevant words to the exclusion of another derasha.

4) We might be able to ask what whoever put forth this derasha would do with the derasha of  לרבות שאפילו ילדתו מחוי. But we cannot necessarily ask this of Rashi, who might derive this lesson from some other source. That is, consider the Midrash Tanchuma I cited above, but in full:

דבר אחר:
אשה כי תזריעאם קדמה האשה, יולדת זכר.
קדם האיש, יולדת נקבה.

אמר רבי אבין הלוי:
רמז לך הכתוב: ואם נקבה תלד.
אם קדם האיש מוליד נקבה.
קדמה האשה יולדת זכר, שנאמר: אשה כי תזריע וילדה זכר.

אמר רבי חייא בר אבא:
לפיכך נתלה הזכר באשה.

ונקבה באיש מנין?
שכך כתיב: הנה ילדה מלכה גם היא בנים לנחור אחיך, את עוץ בכורו וגו', ובתואל ילד את רבקה (ברא' כב כ-כג).
וכן הוא אומר: (ו)פילגש כלב מעכה ילד שבר ואת תרחנה, ותלד שעף אבי מדמנה את שוא אבי מכבנה ואבי גבעא, ובת כלב עכסה (דה"א ב מח-מט).
הוי, נתלו הנקבות באנשים והזכרים בנשים. לכך כתיב: אשה כי תזריע וילדה זכר. 

I am not yet sure how to parse this other derasha mentioned of  ואם נקבה תלד, but note that this is considered a remez. Similarly, isha ki tazria is likely in the realm of remez. They find a more straightforward bolstering of it from the other pesukim cited, namely the children of Nachor, Betuel, and Kalev, where נתלו הנקבות באנשים והזכרים בנשים. This sets the precedent for seeing the message in אשה כי תזריע וילדה זכר, which is why the joining phrase is לכך כתיב.

So too, Rashi in Vayigash just mentions the local prooftext of the attribution of sons to the women and daughters to the men.

Also, see the gemara in Niddah (31a) this is all based on:

אמר רבי יצחק אמר רבי אמי אשה מזרעת תחילה יולדת זכר איש מזריע תחילה יולדת נקבה שנאמר (ויקרא יג, כט) אשה כי תזריע וילדה זכר 

תנו רבנן בראשונה היו אומרים אשה מזרעת תחילה יולדת זכר איש מזריע תחלה יולדת נקבה ולא פירשו חכמים את הדבר עד שבא רבי צדוק ופירשו (בראשית מו, טו) אלה בני לאה אשר ילדה ליעקב בפדן ארם ואת דינה בתו תלה הזכרים בנקבות ונקבות בזכרים 

 (דברי הימים א ח, מ) ויהיו בני אולם אנשים גבורי חיל דורכי קשת ומרבים בנים ובני בנים וכי בידו של אדם להרבות בנים ובני בנים אלא מתוך שמשהין עצמן בבטן כדי שיזריעו נשותיהן תחלה שיהו בניהם זכרים מעלה עליהן הכתוב כאילו הם מרבים בנים ובני בנים והיינו דאמר רב קטינא יכולני לעשות כל בני זכרים אמר רבא הרוצה לעשות כל בניו זכרים יבעול וישנה

Or in English:

R. Isaac citing R. Ammi⁵⁴  stated: If the woman emits her semen first she bears a male child; if the man emits his semen first she bears a female child; for it is said, If a woman emits semen⁵⁵  and bear a man-child.⁵⁶

Our Rabbis taught: At first it used to be said that 'if the woman emits her semen first she will bear a male, and if the man emits his semen first she will bear a female', but the Sages did not explain the reason, until R. Zadok came and explained it: These are the sons of Leah, whom she bore unto Jacob in Paddan-aram, with his daughter Dinah,⁵⁷  Scripture thus ascribes the males to the females⁵⁸  and the females to the males.⁵⁹

And the sons of Ulam were mighty men of valour, archers; and had many sons, and sons' sons.⁶⁰  Now is it within the power of man to increase⁶¹  the number of 'sons and sons' sons'? But the fact is that because they contained themselves during intercourse¹  in order that their wives should emit their semen first so that their children shall be males, Scripture attributes to them the same merit as if they had themselves caused the increase of the number of their sons and sons' sons. This explains what R. Kattina said, 'I could make all my children to be males'. Raba stated: One who desires all his children to be males should cohabit twice in succession.

Further, see how Rashi on the daf interprets the phrase ולא פירשו:

ולא פירשו - את הדבר מנלן:

זכרים בנקבות - בני לאה:

נקבות בזכרים - ואת דינה בתו משום הך דרשה איש מזריע תחלה יולדת נקבה:

Thus, according to Rashi, the derasha is derived from the local pasuk in Vayigash, and not from isha ki tazria veyaleda zachar. This makes sense, since Rabbi Yitzchak citing Rabbi Ami, or Rabbi Assi, represent Amoraim speaking. And it is Rabbi Yitzchak / Rabbi Ammi who connects it to isha ki tazria. But the brayta follows, which includes the Tanna Rabbi Tzadok, gives a different derivation, which is what Rashi is citing there in Vayigash!

Thus, the question of various meforshei Rashi is resolved.