Gemara

63b (Mishnah - R. Yosi): If a woman normally sees at sunrise, she is forbidden only at sunrise;

R. Yehudah permits the entire day.

(Beraisa): If she normally sees on the 20th during the sixth hour, when the 20th comes:

R. Yehudah forbids Bi'ah during the first six hours;

R. Yosi permits Bi'ah before the sixth hour, and forbids during the sixth hour.

If the sixth hour passed and she did not see;

R. Yehudah forbids Bi'ah the rest of the day;

R. Yosi permits from Minchah (after midday) and onwards.

(Mishnah): If she normally sees (R. Yehudah permits the entire day).

Contradiction (Beraisa - R. Yehudah): The entire night is permitted.

Resolution: In the Mishnah, she normally sees at the end of the night. In the Beraisa, she normally sees at the beginning of the day.

(Beraisa #1 - R. Yehudah): She is forbidden before her Veses. She is permitted after it;

Contradiction (Beraisa #2 - R. Yehudah): She is forbidden after her Veses. She is permitted before it.

Resolution: In Beraisa #1, she normally sees at the end of the night. In Beraisa #2, she normally sees at the beginning of the day.

(Rava): The Halachah follows R. Yehudah.

Contradiction (Beraisa - R. Yoshiyah): "V'Hizartem... mi'Tum'asam" forbids a woman shortly before her Veses.

(Rava): She is forbidden (in advance) for an Onah (a night or day(time)).

Suggestion: This is in addition to the Onah in which she expects to see.

Answer: No, it is in the Onah in which she expects to see.

65a (Beraisa - Beis Hillel): If a Besulah saw blood before she was married, we give her the first night (attribute all blood to her Besulim), i.e. a full Onah.

(R. Shimon ben Gamliel): An Onah is a night and half a day.

Question (Beraisa - R. Shimon ben Gamliel citing R. Yosi): To be Metaher a winepress, one puts it in a spring for an Onah;

(R. Chiya bar Aba): An Onah is a day or a night.

(Rabah bar bar Chanah): It is half a day and half a night.

(Rav Shmuel bar Rav Yitzchak): Both refer to 12 hours. R. Chiya discusses Nisan and Tishrei (when the nights and days are equal), and Rabah discusses Teves or Tamuz.

Answer #1: R. Shimon ben Gamliel means a day or night of Nisan or Tishrei, or half a day and half a night in Teves or Tamuz.

Answer #2: Every wedding is delayed until they agree on the Kesuvah. (Half the night will pass before they have Bi'ah.)

Yevamos 62b (R. Yehoshua ben Levi): A man must be Poked (visit) his wife before he goes on a trip - "v'Yadata Ki Shalom Ohalecha (u'Fokadta Navcha)".

Question: "Your desire is to your husband" already teaches that a woman desires her husband when he goes away! (Therefore, he must be Poked her.)

Answer (Rav Yosef): R. Yehoshua's teaching is needed for Samuch l'Vestah.

Rishonim

Rosh (Yevamos 6:10): The Gemara cannot obligate Bi'ah before a man leaves when this is Samuch l'Vestah. The Torah obligates separating Samuch l'Vestah! R. Tam explains that the Gemara discusses verbal intimacy. Most texts say that we discuss when she is Nidah.

Tosfos (Yevamos 62b DH Chayav): All old texts say that we discuss when she is Nidah. Even though Bi'ah is forbidden, it is Simchah for her, since he is leaving. A verse teaches that one who sleeps in a room in which a man and his wife sleep, he expels her from "her house of delight", even if she is Nidah (Eruvin 63b). People changed the text to say "Samuch l'Vestah", for they wanted to explain that Poked refers to Bi'ah. This is wrong. Shevu'os 18b says that the Isur is mid'Oraisa. Also, we obligate Pekidah even if he leaves for Reshus (not a Mitzvah). Even according to the opinion that Samuch l'Vestah is mid'Rabanan, why should Chachamim permit Bi'ah if he leaves for Reshus?!

Ran (Shevu'os 1b DH Oh): If her Veses is during the day, he separates during the day. If it is at night, he separates the entire night. "V'Hizartem" is a mere Asmachta, for we hold that Vestos are mid'Rabanan. Also, Chachamim permitted Samuch l'Vestah before one leaves on a trip. If it were mid'Oraisa, how could Chachamim permit it?!

Poskim

Shulchan Aruch (YD 184:2): At the time of the Veses, one must separate from her for one Onah. He separates only from Bi'ah, but not from other kinds of closeness.

Beis Yosef (DH uv'Sha'as): The Ran and Rashba hold that Vestos mid'Rabanan, and also the Rosh, like I will explain. However, Sefer ha'Terumah says that it is mid'Oraisa, and also Tosfos and the Rosh in Yevamos. However, perhaps they merely mean that it has a support from the Torah.

Shach (5): Most Poskim and Acharonim conclude that this is mid'Rabanan, for Vestos mid'Rabanan.

Pischei Teshuvah (3): The Noda bi'Yehudah (YD 55,56) says that Vestos are mid'Rabanan regarding the concern that she saw at the time of the Veses, but the Torah forbids Samuch l'Vestah, lest she will see. We do not extend Chezkas Taharah into the future. Will she never see?!

Taz (3): The Beis Yosef permits kissing and hugging. We are not concerned lest it lead to Bi'ah, since Bi'ah is forbidden only mid'Rabanan. The Bach says that one who is stringent like Terumas ha'Deshen will be blessed. I say that the Rosh forbids letter of the law. He forbids kissing and hugging during Avelus (YD 383), which is also mid'Rabanan. All the more so we must forbid here, since he has desire when he leaves!

Shach (6): Kissing and hugging are permitted, but one who is stringent will be blessed.

Shulchan Aruch (ibid.): If her Veses is during the day, he separates that entire day, even if the Veses is at the end of the day. He is permitted immediately at night afterwards. Likewise, if the Veses is at the beginning of the day, he separates that entire day, and he is permitted the entire previous night. Similarly, if her Veses is at night, he separates that entire night, and he is permitted the previous and following day. This is whether she fixed the Veses three times or once. This refers to a Veses of days, but not a Veses dependent on a bodily change.

Beis Yosef (DH u'Mah): All the Poskim rule like R. Yehudah. This is unlike is written in the name of Ohr Zaru'a, that one must separate 24 hours. If she normally sees during the day, he separates that day and the night before, and similarly oppositely (if she normally sees at night). There is no source for this. The Agur calls this an excessive stringency.

Taz (2): The Bach says that the Ohr Zaru'a holds that even though the Halachah follows R. Yehudah, it is proper to be stringent. It is astounding to be stringent when the Gemara is explicitly lenient, especially for Vestos mid'Rabanan!

Shach (7): Also Ra'avan holds like Avi'asaf. The Poskim omitted this, because they discuss a Stam day or night. Indeed, in Teves or Tamuz one must calculate relative hours (based on the daylight hours), like we do for Kri'as Shma or Chametz on Erev Pesach.

Question (R. Akiva Eiger): This is unlike Kri'as Shma. There, it is always a quarter of the day, whether it is a long or short day!

Shach (7): Ra'avan agrees that if she normally sees at the beginning of the day, or in the middle, or at the end, he separates only that day. The Gemara and Poskim discuss this. Ra'avan and Ohr Zaru'a discuss one who sometimes sees at the beginning, sometimes in the middle and sometimes at the end. It is as if the entire day is her Veses. Surely, if her Veses is the entire day, she must separate also the night before. The Bach says that one who fears Shamayim should be stringent like the Ohr Zaru'a, and the Terumas ha'Deshen and Maharil bring his opinion.

R. Akiva Eiger: I say that even if she sees at different times, she need not refrain the night before. Chachamim forbade only the day in which she sees, whether she sees in a small part of the day, or the entire day!

Pischei Teshuvah (7): Nekudas ha'Kesef wrote that our women do not have a fixed time to see, so one must separate the entire day and night. Chavas Da'as says from reasoning that one need not be stringent.

Beis Yosef (DH Kasvu): Hagahos Maimoniyos (Hilchos Isurei Bi'ah 4:9) brings from Avi'asaf that the Onah is a day or night of Nisan or Tishrei, or half a day and night of Teves or Tamuz. He holds that Onah is 12 hours of 24 in the day and night. I say that one need not be concerned for his opinion, since not one of the Poskim brought it. Also, the words of the Gemara connote that we are concerned only for the night or day, but not for hours. Hours were mentioned in Perek ha'Ishah only due to the argument of R. Yosi.

Note: In Perek ha'Ishah, there is no mention of hours regarding Onah. Perhaps "ha'Ishah" is a printing mistake, and it should say "Tinokes" (65b). If so, the Beis Yosef answered the coming question of the Bach.

Bach (3, b'Sof): Hagahos Maimoniyos and the Beis Yosef overlooked 65b, which says that Onah for Nidah is 12 hours. We hold like this.

Rebuttal (Taz 2): If it depends on hours, the Isur Onah is when she normally sees, during the day or at night. This is 12 hours only in Nisan and Tishrei, in the middle of day or in the middle of the night! If she sees at the end of the day in Nisan or Tishrei, when are the 12 hours? If they are the 12 hours after she normally sees, we forbid the following night and permit before that time during the day itself. Surely this is wrong, for we forbid the entire day, like R. Yehudah! If the 12 hours are retroactive (before the Veses), when she sees at the beginning of the day, she is permitted during the day after the Veses. Heaven forbid to say so! Similarly, if we forbid six hours before and six hours after, if she saw at the start of the day, the end of the day is permitted. Rather, it must refer to day or night. Chachamim always forbade the day or night, whether it be long or short, based on when she normally sees. Later, they called this Onah, since the day or night is usually 12 hours. This is unlike 65b, which depends only on hours. If a Besulah saw blood and then married, one opinion is Toleh (attributes all blood) for 12 hours after her first Bi'ah to her Besulim. There it cannot depend on the night! If she had Bi'ah at the end of the night, we would be Toleh on Besulim for a very short time, and if one had Bi'ah at the beginning of the night, we would be Toleh for a long time. Therefore, it depends on 12 hours. Here it depends on when she sees Dam Nidah, based on her Veses. Chachamim fixed a uniform Shi'ur for everyone, and forbid the entire day or the entire night. After and before that day or night, she is permitted. Why didn't the Beis Yosef challenge Avi'asaf? Perhaps Avi'asaf himself forbids six hours before and six hours after. However, we rule that she is forbidden the entire day, even if it is a long day.