How to Conceive a Baby Boy- Joy of Text 1:10 by Rabbi Dov Linzer

These sources accompany the (mini) tenth episode of the Joy of Text podcast.

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
§ Rabbi Yitzḥak says that Rabbi Ami says: The sex of a fetus is determined at the moment of conception. If the woman emits seed first, she gives birth to a male, and if the man emits seed first, she gives birth to a female, as it is stated: “If a woman bears seed and gives birth to a male” (Leviticus 12:2).

Hippocrates, On the Generating Seed and the Nature of the Child 4-5

(4) In the case of women, it is my contention that when during intercourse the vagina is rubbed and the womb is disturbed, an irritation is set up in the womb which produces pleasure and heat in the rest of the body. A woman also releases something from her body, sometimes into the womb, which then becomes moist, and sometimes externally as well, if the womb is open wider than normal. Once intercourse has begun, she experiences pleasure throughout the whole time, until the man ejaculates. If her desire for intercourse is excited, she emits before the man, and for the remainder of the time she does not feel pleasure to the same extent; but if she is not in a state of excitement, then her pleasure terminates along with that of the man…. The pleasure experienced by the woman during intercourse is considerably less than the man’s, although it lasts longer. The reason that the man feels more pleasure is that the secretion from the bodily fluid in his case occurs suddenly, and as the result of a more violent disturbance than in the woman’s case.

Another point about women: if they have intercourse with men their health is better than if they do not…

(5) When a woman has intercourse, if she is not going to conceive, then it is her practice to expel the sperm produced by both partners whenever she wishes to do so. If however she is going to conceive, the sperm is not expelled, but remains in the womb. For when the womb has received the sperm it closes up and retains it, because the moisture causes the womb’s orifice to contract. Then both what is provided by the man and what is provided by the woman is mixed together. If the woman is experienced in matters of childbirth, and takes note when the sperm is retained, she will know the precise day on which she has conceived.

מה יעשה אדם ויהיו לו בנים זכרים אמר להם ישא אשה ההוגנת לו ויקדש עצמו בשעת תשמיש אמרו הרבה עשו כן ולא הועילו אלא יבקש רחמים ממי שהבנים שלו שנאמר (תהלים קכז, ג) הנה נחלת ה' בנים שכר פרי הבטן
The sages of Alexandria further asked: What should a person do to have male children? Rabbi Yehoshua said to them: He should marry a woman who is fit for him and sanctify himself by acting modestly at the time of sexual intercourse. The sages of Alexandria said to Rabbi Yehoshua: Many people have done so, and it did not help them. Rabbi Yehoshua said: Rather, they should pray to receive sons from the One to Whom sons belong, as it is stated: “Behold, children are a heritage of the Lord; the fruit of the womb is a reward” (Psalms 127:3).
ויקדש עצמו - לשמש בצניעות:

And sanctify himself – to have sex with modesty.

שמשהין - להוציא את הזרע:

That they tarry – from ejaculating the semen.

בעלי הנפש שער הקדושה

ומי שאומד את עצמו שיוכל לעשות כך ולא תכנס עליו מחשבה אחרת, והוא משהא עצמו כדי שתהנה האשה מן המעשה ותזריע תחילה, מתכוין לעשות מצוה ועושה אותה והקב”ה נותן לו שכרו בבנים זכרים

Raavad, Ba’alei Hanefesh, Gate of Holiness

Someone who assesses himself that he can act thusly (“delaying on the womb”) and no foreign thought will enter his mind, and he “delays on the womb” so that his wife derives pleasure from the act and gives forth seed first – such a person is intending to do a mitzvah and he is doing a mitzvah, and God will give him his reward with male children.

תניא נמי הכי גם בלא דעת נפש לא טוב זה הכופה אשתו לדבר מצוה ואץ ברגלים חוטא זה הבועל ושונה איני והאמר רבא הרוצה לעשות כל בניו זכרים יבעול וישנה לא קשיא כאן לדעת כאן שלא לדעת:
That was also taught in a baraita: “Also, without knowledge the soul is not good”; this is one who forces his wife to perform the conjugal mitzva. “And he who hastens with his feet sins”; this is one who has intercourse with his wife and repeats the act in a manner that causes her pain or distress. The Gemara is surprised by this teaching: Is that so? But didn’t Rava say: One who wants all his children to be males should have intercourse with his wife and repeat the act? The Gemara answers: This is not difficult: Here, where Rava issued this advice, he was referring to a husband who acts with his wife’s consent. There, the baraita that condemns this behavior is referring to one who proceeds without her consent.