Yevamot

Surely Tamar  conceived from a first contact! The other answered him: Tamar exercised friction with her finger;  for R. Isaac said: All women of the house of Rabbi who exercise friction  are designated Tamar. And why are they designated Tamar? — Because Tamar exercised friction with her finger. But were there not Er and Onan?  — Er and Onan indulged in unnatural intercourse. An objection was raised: During all the twenty-four months  one may thresh within and winnow without;  these are the words of R. Eliezer. The others said to him: Such actions are only like the practice of Er and Onan!  -Like the practice of Er and Onan, and yet not [exactly] like the practice of Er and Onan: 'Like the practice of Er and Onan', for it is written in Scripture, And it came to pass, when he went in unto his brother's wife, that he spilt it on the ground;  and 'not [exactly] like the practice of Er and Onan', for whereas there it was an unnatural act, here it is done in the natural way. [The source for] Onan's [guilt] may well be traced, for it is written in Scripture, That he spilt it on the ground;  whence however, [that of] Er? — R. Nahman b. Isaac replied: It is written, And He slew him also,  he also died of the same death. [The reason for] Onan's [action] may well be understood, because he knew That the seed would not be his;  but why did Er act in such a manner? — In order that she might not conceive and thus lose some of her beauty. Our Rabbis taught [The woman also] with whom [a man shall lie],  excludes a bride;  so R. Judah. But the Sages say: This excludes unnatural intercourse. Said Hon son of R. Nahman to R. Nahman: Does this imply that R. Judah is of the opinion that the Torah had consideration for the bride's make-up?  — The other replied: Because no woman conceives from her first contact — 14 On what principle do they differ? — The Rabbis are of opinion that 'carnally'  excludes the first stage of contact, and 'with whom'  excludes unnatural intercourse; but R. Judah is of the opinion that the exclusion of unnatural intercourse and the first stage of contact may be derived from 'carnally'.  while 'with whom'  excludes a bride. When Rabin came  he stated in the name of R. Johanan: A woman who waited ten years after [separation from] her husband, and then remarried, would bear children no more. Said R. Nahman: This was stated only in respect of one who had no Intention of remarrying: if, however, one's intention was to marry again she may conceive. Raba said to R. Hisda's daughter:  The Rabbis are talking about you. She answered him: I had my mind on you. A woman once appeared before R. Joseph, and said to him: Master, I remained unmarried after [the death of] my husband for ten years and now I gave birth to a child — He said to her: My daughter, do not discredit the words of the Sages. She thereupon confessed, 'l had intercourse with a heathen'. Samuel said: All these women,  with the exception of a proselyte and an emancipated slave who were minors, must wait three months.  An Israelitish minor, however, must wait three months. But how [was she separated]?  If by a declaration of refusal,  surely. Samuel said that she  need not wait!  And if by a letter of divorce, surely Samuel has already stated this once! For Samuel said: If she' formally refused him  she need not wait three months; if he gave her a letter of divorce she must wait three months!  -[It  was] rather in respect of unlawful intercourse,