It is derived from a verbal analogy between the terms entering and entering. The verse states in the context of a prohibition: “A mamzer shall not enter into the assembly of the Lord” (Deuteronomy 23:3), and in the context of a prohibition derived from a positive mitzva: “The children that are born to them of the third generation may enter into the assembly of the Lord” (Deuteronomy 23:9). Consequently, these types of prohibitions are equated.

The Gemara poses another question: From where do we derive that the initial stage of intercourse is considered sexual intercourse with regard to the prohibition against a yevama having intercourse with a man from the general public? The Gemara answers that there is no need for an independent source in this case: If you are asking according to the one who said that this is an ordinary prohibition, it is a prohibition like any other. If you are asking according to the one who said that this is a positive mitzva, it is a positive mitzva like any other.

Rather, the question is as follows: From where do we derive that a yevama is acquired by her yavam via the initial stage of intercourse? The Gemara answers: It is derived from a verbal analogy between the words entering and entering. This verb is used with regard to ordinary Torah prohibitions, as mentioned above, and also with regard to levirate marriage, in the verse “Her brother-in-law will have intercourse with her” (Deuteronomy 25:5).

The Gemara asks further: From where do we derive that a woman is betrothed to her husband through the initial stage of intercourse? The Gemara answers: It is derived from a verbal analogy between the words taking and taking. With regard to betrothal, the verse states: “When a man takes a wife and marries her” (Deuteronomy 24:1). This verb is also used with regard to forbidden intercourse, as in the verse: “And if a man shall take his sister” (Leviticus 20:17).

§ Rava said: Now that it has been established that the initial stage of intercourse is considered an act of sexual intercourse, why do I need the expression “cohabitation with seed” (Leviticus 19:20) that the Merciful One writes with regard to a designated maidservant; the expression “cohabitation with seed” (Leviticus 18:20) written with regard to a married woman; and the expression “cohabitation with seed” (Numbers 5:13) written with regard to a sota?

The Gemara explains that the expression is necessary with regard to a designated maidservant as we said above (55a), because it indicates that one is liable to receive punishment only for a complete act of intercourse with a designated maidservant but not for the initial stage of intercourse. With regard to a married woman, the word seed excludes one who has intercourse with a dead organ, i.e., one that is not erect, as this cannot lead to childbirth.

The Gemara questions this resolution: This works out well according to the one who said that one who has intercourse while his organ is dead with those with whom relations are forbidden, is exempt, as this is not considered an act of intercourse. However, according to the one who said that he is liable, what is there to say? Rather, according to this opinion, the verse excludes one who has intercourse with a dead woman. As it might enter your mind to say: Since after death she is also called her husband’s kin, say that one who had intercourse with her should be liable to receive punishment for committing adultery with a married woman. It therefore teaches us that intercourse with a dead woman is not considered intercourse at all.

The Gemara addresses the third case: Why do I need the expression cohabitation with seed in the context of a sota? It is needed for that which is taught in a baraita, that the expression a cohabitation with seed excludes something else. The Gemara asks: What is this something else? Rav Sheshet said: It excludes a case where the husband was jealous with regard to her and warned her not to seclude herself and have atypical, i.e., anal, sexual intercourse with another man. Rava objected to this explanation and said to him: It is written: “The cohabitations of a woman” (Leviticus 18:22), indicating that there are two types of intercourse with a woman, and the same halakha applies to both.

Rather, Rava said: It excludes a situation where the husband was jealous with regard to her and warned her not to seclude herself with another man and engage in intimate contact by way of other limbs. The verse indicates that the wife does not become prohibited to her husband if she secludes herself with the man after this warning. Abaye said to him: Does the Merciful One prohibit a woman to her husband due merely to licentious behavior without sexual intercourse? Since this behavior would not render a woman prohibited to her husband, it is obvious that a warning that explicitly mentions this behavior is insufficient to cause the woman to become a sota if she then secludes herself with the man.

Rather, Abaye said: It excludes a case where he was jealous with regard to her and warned her not to seclude herself with another man and kiss, i.e., have external contact of the sexual organs. The Gemara asks: This works out well according to the one who said that the definition of the initial stage of intercourse is the insertion of the corona; therefore, mere external contact is not considered sexual intercourse. However, according to the one who said that the definition of the initial stage of intercourse is a kiss, what is there to say?

Rather, the expression: Something else, in the baraita, is actually referring to a case where the husband was jealous with regard to her and warned her not to seclude herself with another man and engage in intimate contact by way of other limbs. And it is necessary to state that the woman does not become prohibited to her husband as a sota in this case, as it might enter your mind to say that the Merciful One made this halakha dependent on the husband’s objection, as it is his decision to warn his wife, and since he objects to contact of this nature, she becomes a sota if she secludes herself after this warning. The Torah therefore teaches us that this is not considered a warning.

§ The Gemara returns to the precise definition of the initial stage of intercourse. Shmuel said: The definition of the initial stage of intercourse is a kiss, i.e., external contact of the sexual organs. Shmuel explains: This is comparable to a person who places his finger on his mouth; it is impossible that he not press the flesh of his lips. Similarly, when there is contact of the sexual organs, there will certainly be at least a small amount of penetration, and this is considered an act of sexual intercourse.

When Rabba bar bar Ḥana came from Eretz Yisrael, he said that Rabbi Yoḥanan said: The completion of intercourse stated with regard to a designated maidservant is the insertion of the corona, and no more. Rav Sheshet raised an objection based upon the following baraita: The phrase cohabitation with seed indicates that one is liable to receive punishment only for a complete act of sexual intercourse. What, does this not refer to the complete insertion of the member? The Gemara responds: No, it is possible that it is referring to the complete insertion of the corona.

When Rav Dimi came from Eretz Yisrael he said that Rabbi Yoḥanan said: The definition of the initial stage of intercourse is the insertion of the corona. They said to him: But Rabba bar bar Ḥana did not say so, as he taught that Rabbi Yoḥanan said that the insertion of the corona constitutes a complete act of sexual intercourse and is not considered merely the initial stage of intercourse. He said to them: Either he lied or I am lying. There is clearly a contradiction, and one of us cited Rabbi Yoḥanan’s opinion incorrectly.

When Ravin came from Eretz Yisrael he said that Rabbi Yoḥanan said: The definition of the initial stage of intercourse is the insertion of the corona. The Gemara comments: He certainly disagrees with Rabba bar bar Ḥana, who cited Rabbi Yoḥanan as stating that insertion of the corona constitutes a complete act of sexual intercourse. Shall we say that he also disagrees with Shmuel, who defined the initial stage of intercourse as external contact of the sexual organs?

The Gemara responds: No; it is possible that there is no dispute between them, and Ravin said that Rabbi Yoḥanan calls the entire process from a kiss until the insertion of the corona the initial stage of intercourse, while anything beyond that point is a complete act of sexual intercourse.

When Rav Shmuel bar Yehuda came from Eretz Yisrael he reported that Rabbi Yoḥanan said: The definition of the initial stage of intercourse is the insertion of the corona, whereas a complete act of sexual intercourse is literally a complete act of sexual intercourse, i.e., insertion of the male organ beyond the corona.