Kiddushin, Chapter Two, Mishnah 5. The mishnah deals with a man who betroths a woman on condition - that she has no vows upon her, or that she has no blemishes - and with the status of the betrothal when it turns out that the condition was not met.
One who betroths on condition that she has no vows:
"HaMekadesh es haIshah al menas she'ein aleha nedarim, venimtze'u aleha nedarim - einah mekudeshes" - one who betroths a woman on condition that there are no outstanding vows upon her, and it turned out that there are vows upon her, the betrothal is not valid.
However, if after that conditional betrothal he married her without qualification, without repeating his condition, "venimtze'u aleha nedarim - tetze shelo bekesubah": she goes out with a get, but without a kesubah. There are two reasons for this:
Why she needs a get: we are concerned that since he married her without repeating the condition, he waived it. A man does not want his relations with his wife to be relations of licentiousness, a forbidden union lacking the sanctity of betrothal, and therefore he certainly gave up his condition and had relations for the purpose of betrothal, even if she should turn out to have vows upon her. Because of this concern she is not released without a get, since perhaps there was a valid betrothal here.
Why she loses her kesubah: in monetary matters the husband can claim that he never waived anything, and that his condition stands in force.
It is worth noting that this halachah applies even if he made no condition at all at the time of the betrothal that she has no vows upon her. The very fact that a man does not want a wife who has vows upon her is enough for him to be able to claim that this is not the sort of woman he intended, and she goes out with a get and without a kesubah.
On condition that she has no blemishes:
"Al menas she'ein bah mumin, venimtze'u bah mumin - einah mekudeshes" - if he betrothed her on condition that she has no physical blemishes, and those significant blemishes were found in her, she is not betrothed, for such was the condition of the betrothal.
If he then married her without qualification, without repeating the condition, "venimtze'u bah mumin - tetze shelo bekesubah" - she goes out with a get, for that very same reason: we are concerned that in order that his relations should not be relations outside the framework of marriage, he intended to marry her through this act. But she loses her kesubah, since in monetary matters the husband can claim: I did not agree to this marriage if she has blemishes.
Which blemishes disqualify:
The conclusion of the mishnah is: all the blemishes that disqualify kohanim - every blemish severe enough to disqualify a kohen from serving in the Beis HaMikdash, as detailed in the Torah in Parashas Emor and also in Maseches Bechoros - are the ones that disqualify a woman when he stipulated that she be free of blemishes.
Here too, as in the first part of the mishnah, even if he betrothed her without stipulating that she has no blemishes, he can afterward claim regarding the kesubah that he did not wish to marry a woman with blemishes, and therefore she goes out without a kesubah.
In summary: one who betroths on condition that the woman has no vows upon her or no blemishes, and they were found in her - she is not betrothed. If he married her without qualification, without repeating his condition, we are concerned that he may have waived the condition so that his relations should not be relations of licentiousness, and therefore she goes out only with a get; but regarding money he can claim that he did not waive it, and therefore she goes out without a kesubah. The definition of the blemishes is derived from the blemishes that disqualify kohanim, and this law applies even when he made no condition to begin with.