(Mishnah): Even though a woman (Rashi - with a Veses) is Dayah Shaitah, she must check herself (for Taharos), except for a Nidah (during the seven days) or a Yoledes in Yemei Tohar. (On days 8-40 after giving birth to a boy, or days 15-80 after giving birth to a girl, any blood she sees is called Dam Tohar. It is not Metamei her.)

And one who checks with Edim (cloths) at the time of Bi'ah, except for a Yoledes during Dam Tohar or a Besulah, for her blood is Tahor.

She must check herself twice [daily], in the morning and evening, and before Bi'ah.

In addition to these, a Kohenes [must check herself] before eating Terumah;

R. Yehudah says, also when she finishes eating Terumah.

(Gemara): Our Mishnah means, except for a Nidah who did not interrupt in Taharah (she has been seeing every day. If not, even though in any case she is Temei'ah, she would check for the sake of fixing a Veses.

(Mishnah): And one who checks with Edim at the time of Bi'ah.

Our Mishnah means that she must check with Edim at the time of Bi'ah.

And [except for] a Besulah, for her blood is Tahor.

Our Mishnah [connotes that her blood is Tahor as long as she sees due to her Besulim. It] discusses a girl who did not reach the age to see, and she married. (If she reached the age to see, Beis Hillel are Metaher only for four nights.)

(Shmuel): (In a Mishnah, Beis Hillel say that if she already saw before Nisu'in, she is permitted to have Bi'ah the entire night; we attribute all the blood to Besulim.) She gets the night and [half of the following] day - an Onah, and part of an Onah.

If she ceased [seeing Dam Besulim], and afterwards saw, she is Tamei.

If the appearance of her blood changed, she is Tamei (surely the new blood is Dam Nidah).

(R. Ze'ira): This is when it did not change due to Bi'ah (i.e. she saw without Bi'ah), but if it changed due to Bi'ah, she is Tahor.

Support (R. Yosi - Mishnah): And [except for] a Besulah, for her blood is Tahor. This teaches that [she need not check herself at the time of Bi'ah, for even] if the appearance will change due to Bi'ah, she is Tahor;

If you will say that if the appearance changes due to Bi'ah, she is Tamei, she should have Bi'ah with Edim, lest the appearance change due to Bi'ah, and she will be Tamei!