What is the meaning of "va'Tizna [Alav Pilagsho]"?
R. Evyasar (Gitin 6b): He found a fly in his Mazon (food, which she prepared for him).
R. Yonason (Gitin 6b): He found a hair. Some say that it was in his food, and some say, in the place of Bi'ah.
Rashi: She had Bi'ah [with another man] outside his house. 1 Zenus always refers to leaving, like Targum Onkelos (of Zonah - Bereishis 34:31) 'Nafkas Bara'. She leaves her husband to love others.
Radak citing Targum Yonasan: U'Vesaras. This is like Targum Onkelos of "Davar Hashem Bazah" (Bamidbar 15:31). She disgraced him and left him and went to her father's house.
Malbim: Refer to 19:2:2:3. Also, "va'Yakam Ishah" (verse 4) implies that there was no Zenus, for he is still called her husband. According to the opinion that a Pilegesh has Kidushin (refer to 8:31:1:2), Zenus forbids her. (What is the support? Even if she is forbidden, he is still her husband! - PF)
Why does it say "va'Tizna Alav"?
Radak #1: "Alav" means 'in front of him', i.e. she did not conceal the Zenus.
Radak #2: It means while she was still with him. This is like "va'Yavo'u ha'Anashim Al ha'Nashim" (Shemos 35:22); it is as if it says "Im". Va'Telech me'Ito (is not the Perush of va'Tizna. Rather,) he got angry at her, and she went to her father's house.
Malbim: If she was Mezanah, it should have said me'Alav! Rather, this supports Chazal, who say that she merely did something against his will (refer to 19:2:1:1,2).
How long was she in her father's house?
Radak: It was a year and four months, as if it said Yamim v'Arba'ah Chodoshim. We find like this (the Vov is omitted) - "Shemesh Yare'ach" (Chabakuk 3:11).
Radak citing Targum Yonasan: It was four months; this is the Perush of "Yamim".
