Sotah, Chapter 5, Mishnah 1:
Our mishnah deals with two matters: the effect of the bitter waters on the adulterer, and the woman becoming forbidden to both of them - to her husband and to the man with whom she sinned.
The effect of the waters on the adulterer:
"Keshem shemayim bodkin osah" - just as those bitter waters of the sotah examine her and clarify her judgment, and have the power to bring about her death, "kach hamayim bodkin oso" - so too the waters have their effect on the adulterer as well. In other words, he does not emerge unscathed; he too will die from the waters.
"Shene'emar: uva'u" - from the extra vav in the word "uva'u" ("and these waters shall enter into her") we learn that the effect applies to the adulterer as well - not to the husband, but to the adulterer, in addition to the adulteress.
The prohibition upon the adulterer:
"Keshem she'asurah laba'al kach asurah labo'el" - just as the adulteress becomes forbidden to her husband, so too she becomes forbidden to the man with whom she sinned. That is, if she was divorced or her husband died, she may not marry him. "Shene'emar: nitma'ah venitma'ah" - the extra vav teaches that the law applies to the adulterer as well. "Divrei Rabbi Akiva" - this is the opinion of Rabbi Akiva.
The source for this law - two approaches to the derivation:
"Amar Rabbi Yehoshua: kach hayah doresh Zechariah ben HaKatzav" - Zechariah ben HaKatzav agreed with Rabbi Akiva's approach, that it is the extra vav that teaches us to include both of them: both regarding the effect of the waters on the adulterer, and regarding her becoming forbidden to him.
"Rabbi omer" - in Rabbi's opinion, the source for her becoming forbidden both to her husband and to the adulterer is not the extra vav, but rather the repetition in the wording of the passage: "Shnei pe'amim amurim baparashah" - "im nitma'ah" is stated twice, "echad laba'al" - one teaches that she is forbidden to her husband, "ve'echad labo'el" - and the second teaches that she is forbidden to the adulterer.
In summary: In this mishnah we learned that the examination by the bitter waters and the woman's becoming forbidden are not limited to the adulteress and her husband alone, but apply to the adulterer as well. According to Rabbi Akiva, and as Zechariah ben HaKatzav also expounded, this is derived from the extra vav in the words "uva'u" and "venitma'ah"; according to Rabbi, it is derived from the repetition of the phrase "im nitma'ah" in the passage - one for the husband and one for the adulterer.