The Gemara in Shavuot 30b states that a talmid chacham who knows testimony is not obligated to testify in a lesser Beit Din if he finds it disgraceful. This is based on the principle in Brachot 19b, "Gadol kvod habriot" (Self-dignity is very important), which is derived from the pasuk regarding hashavat aveidah, "vehitalamta" (hide yourself). The Gemara concludes that this is true only regarding money, but regarding prohibitions (such as to testify that a woman's husband is still alive. Rashi) -- "There is neither wisdom nor understanding nor counsel against Hashem." (Mishlei 21:30)

Tosfot (s.v. aval) asks that from the Gemara Brachot it would seem that we say gadol kvod habriot even in certain cases of prohibition. The Gemara there states that if one finds kilayim (shatnez) in his clothes, he must remove them even in the marketplace (even though he will be embarrassed in public), because "There is neither wisdom," etc. The Gemara questions this halacha from two sources. First, from hashavat aveida, to which it answers that money is different (like our Gemara). Second, from a person who encounters a met mitzvah, who must bury the corpse even though he will miss out on korban Pesach and mila, which are issurim. The Gemara answers "shev ve'al taaseh shani," that violation through passivity is different from active violation. Most Rishonim interpret this to mean that he is passive in being unable to offer the korban Pesach, while wearing kilayim is considered active, so we don't apply gadol kvod habriot.

Tosfot thus asks, our Gemara distinguishes between testimony regarding money and testimony regarding issurim, but according to the Gemara Brachot -- even regarding issurim we say gadol kvod habriot in passive circumstances, such as declining to testify! Tosfot gives two answers. First, he distinguishes between a big and little disgrace. Met mitzvah is considered a great disgrace, and therefore it is permissible to neglect korban Pesach in a passive manner in order to bury it. Similarly, the Gemara asks from kilayim, since it also involves a big disgrace. To testify in a lesser Beit Din, however, is not such a big disgrace. Therefore, it is similar to hashavat aveidah, and for a lesser disgrace we only say gadol kvod habriot regarding money, even in passive circumstances.

Tosfot's second answer does not distinguish between a big and little disgrace, but only between active and passive circumstances. Although our case of would seem to be passive, since the talmid chacham is passively refraining from testifying, yet, since if the women will remarry she will violate actively -- it is considered as active for the talmid chacham also.

What exactly is this distinction between active and passive violation? R. Elchanan Wasserman, in Kovetz Shiurim, offers two explanations. One, that an active violation is more severe than a passive one. Thus, in a case involving kvod habriot, one cannot violate actively, but can do so passively. The second possibility is that kvod habriot is on par with a transgression, and so, when faced by a clash between kvod habriot and a violation -- the person should maintain a neutral stance and be passive. (This approach is somewhat problematic in the case of met mitzvah, where he actively buries the dead, and only the ensuing neglect of korban Pesach is passive. We have to answer that since the person is to take a neutral stance on the issue of kvod habriot, he just does the mitzvah facing him without relating to the consequences.) Regarding kilayim, however, since wearing it is considered an active violation -- to continue wearing it would be showing a preference to kvod habriot.

The practical difference between these two explanations is Tosfot's second answer, where the person himself is passive, but his passivity leads to an active violation by others. If the distinction is that an active violation is more severe, then in a clash between your own disgrace and the woman's active violation -- we don't say gadol kvod habriot, since a person who can prevent another from violating and doesn't do so is held accountable, as if he himself violated. However, according to the second explanation, that a person should maintain a passive stance and do nothing -- he need not testify. Thus, R. Elchanan's second explanation cannot accept Tosfot's second answer, that testimony about a woman's husband is considered active, but rather must follow the first answer that differentiates between degrees of disgrace.

The Achronim point out that these two explanations are essentially a dispute between the Rambam and the Rosh. The Rambam (Hil. Kilayim 10:29) writes that if someone sees another person wearing kilayim, he must remove it from him, whereas the Rosh only talks about the person himself. This dispute is brought in the Responsa of the Noda Biyhuda (O.C. 35) in the following case. Someone committed adultery with the wife of an important person, of a Rabbinic family, and later married their daughter. Does he have to inform his father-in-law of his wife's adultery, since she is prohibited to him, or can we apply gadol kvod habriot since this will cause a great disgrace to the family? The Noda Biyhuda discusses this at great length, and writes that it depends on the dispute between the Rambam and Rosh. He is being passive, but meanwhile his father-in-law is violating actively. The Shaagat Aryeh, as well, writes that these two answers of Tosfot depend on this dispute between the Rambam and Rosh.

However, the Sefer "Bod Kodesh," by the Rosh Hayeshiva of Ponovez, suggest an alternate understanding of the Rambam. The Rambam writes (Hil. Kilayim 10:29):

One who sees kilayim that is prohibited by the Torah on his friend, even if he is walking in the marketplace, must jump up and tear it off him immediately, even if it was his Rav who taught him wisdom, since kvod habriot doesn't push off a lav which is explicit in the Torah. [Some infer that had it been derabanan it would push off the prohibition.]Why is it pushed off by hashavat aveidah? Because it is a lav of money.Why is it pushed off by tumat met [mitzvah]? Since the Torah specifically wrote "vela'achoto," it was learned by tradition that one does not defile for his sister, but does defile for a met mitzvah. Now, the Gemara in Brachot asks two questions and provids two answers. It asks from hashavat aveidah, and answers that there is a pasuk of "vehitalamta" and we cannot learn issurim from money. It asks from met mitzvah, and answers that it says "vela'achoto," and "passive violation is different." [Tosfot in Brachot asks, why do we need a special pasuk, "vehitalamta," for hashavat aveidah -- why not learn it by analogy from met mitzvah? He answers with the distinction between a big and little disgrace, that perhaps the Torah ruled gadol kvod habriot only for the great disgrace of met mitzvah, but not for the little disgrace of hashavat aveidah. Conversely, why not learn, then, met mitzvah from hashavat aveidah? Since hashavat aveida is only money and we cannot learn from it to issurim. Therefore, we also need the pasuk for met mitzvah.] The Rambam, however, doesn't quote the conclusion of the Gemara, but just quotes the pasuk of "vela'achoto." He does not explain, however, why we do not learn from it! The Tumim says that the Achronim have no answer for this.

The truth is that distinction between passive and active violation is not in explicit in the Gemara. The classical understanding of the Rishonim is forced to assume that continuing to wear kilayim must be active, which is hard to understand. The Ritva explains that since he should remove it and doesn't -- it is considered active. [This is somewhat difficult. How is this different from notar, for which there are no lashes since it is a passive violation, even though the person should have eaten it? The footnote to the Ritva points out that the Ritva adds that he was active in putting on the kilayim initially.] Apparently, the Rambam couldn't accept this definition that kilayim is considered active. Since it, too, is also passive, the Gemara must have meant something else.

The Rambam must have interpeted the Gemara's conclusion, that met mitzvah pushes off korban Pesach since it is passive, to mean that Pesach is only an aseh (positive command), whereas kilayim is a lav. All the other Rishonim learn that the contrast to passive is active, while the Rambam learns that the contrast is a lav. This is implied by the language of Rambam -- "Because it is a lav of money." Normally the Gemara is simply interpreted as distinguishing between money and issur. Why, then, why did the Rambam mention that it is a "lav" of money? (I.e., that in addition to the positive command of hashavat aveidah there is also a lav to avoid returning it.)

According to this new interpretation, we understand the Rambam well. Where is the Gemara's final distinction? The Rambam doesn't learn it as a distinction between passive and active, because of the difficultly of kilayim, but instead learns that Pesach and mila are mitzvot aseh, while kilayim is a lav, and we don't say gadol kvod habriot by a lav. This is further emphasized in the beginning of Rambam, "since kvod habriot doesn't push off a lav which is explicit in the Torah." What, then, is the question from hashavat aveida, which is an aseh? The Gemara was asking that it also has a lav, but answered that still, it is only a lav of money.

What emerges is that there are two interpretations of the Rambam why one has to remove another person's kilayim. One, the classical understanding of the Noda Biyhuda and Shaagat Aryeh, that it is considered an active violation by the other person. Two, the novel interpretation of the Bod Kodesh, since it is a lav and we never apply gadol kvod habriot in the face of lav.

The practical difference between these two approaches will be, for example, if a person needs to go burn his chametz, which entails a lav, and encounters a met mitzvah. The Magen Avraham (444:11) writes that should tend to the dead and not burn the chametz, because it is a passive violation of the prohibition of chametz, and gadol kvod habriot. This ruling, however, is according to the classical interpretation, based on Tosfot, that a passive violation is less severe. According to our new interpretation of the Rambam, however, since by not burning chametz one violates a lav -- even though it is the kind of lav that one violates passively -- we do not say gadol kvod habriot, and he should have to continue on to burn the chametz. (Before Pesach he can avoid the prohibition of chametz by bitul, but the problem would arise on Pesach itself.)

The Achronim link the Rambam, that one must remove the kilayim of his friend, with the second answer of Tosfot that has to testify in order to save the woman from violating actively. There could be a big difference, though. In the case of kilayim, there is an initial conflict between kvod habriot and the prohibition of kilayim for person wearing the clothing. There is another, secondary, problem for the bystander, who has the responsibility of rebuke, "hocheach tocheach." For this, he must first determine if the person himself is in violation. The person himself must remove the kilayim -- whether based on Tosfot's rationale that wearing kilayim is considered an active violation, or based on the Rambam's criterion that it is a lav. Thus, after it is determined that the person is in violation by continuing to wear it, other people must remove it also, since the responsibility of rebuke depends on the wearer's obligation. Thus, the bystander cannot say that he is being passive and apply gadol kvod habriot. Regarding testimony, however, this is not so. Here, the talmid chacham has a responsibility to testify, but has an issue of his own kvod habriot on other side, so perhaps he can remain passive.

Thus, the Achronim's contention that the Rambam is like the second answer of Tosfot -- that testifying for others is comparable to taking off clothes from another -- is not completely valid. By kilyaim, we first determine that the person is in violation, and then the obligation of rebuke requires the bystander to act. But here, regarding testimony, the clash focuses on the witness himself, so perhaps even the Rambam would say gadol kvod habriot, and he doesn't have to testify. (Perhaps he would still have to rebuke the woman privately that her husband is still alive, but he would not have to testify.)