At least when it comes to talking about sex, the rabbis are not Puritans TB Yevamot 34

Can a virgin become pregnant due to her first intercourse? According to day’s daf TB Yevamot 34, no. “The Gemara asks: But isn’t it known that a virgin woman does not become pregnant from her first sexual act?” (Sefaria.org translation) We know that is not medically true, but let’s analyze Tamar’s story found in Genesis 38. From the simple reading of the story, she did become pregnant from her first sexual encounter. Let’s see how the rabbis understood what took place.

Here is some background first, but I encourage you to read the entire chapter. (https://www.sefaria.org/Genesis.38?ven=The_Contemporary_Torah,_Jewish_Publication_Society,_2006&vhe=Miqra_according_to_the_Masorah&lang=bi&aliyot=0)

 Judah had three sons, Er, Onen, and Shelah. Tamar married Er. Er was evil in God’s sight and died without sons; consequently, Judah told Onen to take Tamar in a levirate marriage. Onen refused to fulfill his obligation which displeased God and Onen died without sons. Not knowing the reason why his first two sons died, Judah was hesitant to give Tamar to Shelah for perhaps she was the cause of their deaths. When Tamara saw that Judah was not giving her to Shelah, she took matters into her own hands. She dressed in harlot’s clothing. Judah saw on the side of the road and he engaged her services without knowing that she was his daughter-in-law. They engaged in intercourse only one time. Tamar became pregnant with Judah’s child. That’s all you have to know for today’s daf, but you have to read how the story ends.

The Gemara cites this story if and then immediately rejects it as proof that a virgin can become pregnant from her first sexual act.

“But didn’t Tamar become pregnant from the first act of intercourse, despite the fact that she was a virgin at the time of her sexual act with Judah? Rav Naḥman said: Tamar broke her hymen with her finger prior to intercourse, and it is due to this that she became pregnant from the first act of intercourse, as Rabbi Yitzḥak said: All of those women from the household of Rabbi Yehuda HaNasi who break their hymens are named Tamar by nickname. And why are they named Tamar? They are called this on account of Tamar, who broke her hymen with her finger. The Gemara wonders about the proof from Tamar itself: But weren’t there Er and Onan, her previous husbands, who presumably engaged in sexual intercourse with her? The Gemara responds: Er and Onan engaged in sexual intercourse in an atypical manner, i.e., anal intercourse, and therefore she was still a virgin.” (Sefaria.org translation)

Rabbi Eliezer suggests that a husband uses coitus interruptus with his wife, a nursing mother, as a means of birth control.

“The Gemara raises an objection from a baraita: After a woman gives birth, her husband penetrates inside and spills his semen outside for the entire twenty-four months during which the baby is breastfeeding, so that his wife not become pregnant, as that would terminate her milk production and the child might die. This is the statement of Rabbi Eliezer. They said to him: These acts are nothing other than acts similar to those of Er and Onan, which are prohibited. Regardless, it can be deduced from here that Er and Onan engaged in normative sexual intercourse with Tamar, only they did not fully complete the sexual act.

“Gemara answers: The Tosefta actually means that what they did was similar to the act of Er and Onan in some ways, but not similar to the act of Er and Onan in other ways. The Gemara elaborates: It was similar to the act of Er and Onan in that there was a spilling of semen, as it is written: “And it came to pass when he had intercourse with his brother’s wife, that he spilled it on the ground” (Genesis 38:9). Yet it was not similar to the act of Er and Onan, as there Er and Onan engaged in sexual intercourse in an atypical manner, i.e., anal intercourse, while here the Tosefta is referring to sexual intercourse in a typical manner.

“The Gemara continues to clarify what took place: Granted, Onan engaged in unnatural sexual intercourse with her, as it is written with regard to his act: “That he spilled it on the ground” (Genesis 38:9). However, from where do we derive that Er engaged in unnatural sexual intercourse with her? Rav Naḥman bar Yitzḥak said: As it is written with regard to Onan: “And He slew him also” (Genesis 38:10). This indicates that he, too, died the same death for performing the same transgression as his brother. The Gemara asks: Granted, Onan engaged in anal intercourse because he did not want Tamar to give birth as “he knew that the seed would not be his” (Genesis 38:9). However, with regard to Er, what is the reason he acted in this way? The Gemara responds: He did so in order that she not become pregnant and become less beautiful as a result of her pregnancy.” (Sefaria.org translation)

At least when it comes to talking about sex, the rabbis are not Puritans.