Halakhah su Deuteronomio 19:15

But if they see that the sinner is one of the foolish scoffers who hate their reprovers, as it is written (Mishlei 9:8): "Do not reprove the scoffer, lest he hate you," and their words will certainly not be accepted, and men such as these readily return to their folly, so that he may very likely come to sin again — if so, it is better for them if they tell it to the judges of the city, so that they chastise him for his sin and keep him from future transgression. And it would seem that the same holds true for [telling] the relatives of the sinner if [we know that] their words [of reproof] will be accepted by him [see Be'er Mayim Chayim]. And the entire intent of the teller should be for the sake of Heaven and in zeal for the L–rd, and not because of their hatred of him for something else. And the judges, too, should chastise the sinner in secret and not "whiten his face" in public, as it is written (Vayikra 19:17): "Reprove shall you reprove your neighbor, but do not bear sin because of him." And all this if they saw him with [i.e., if they were] two witnesses, but if he were a single witness, he may not testify against his friend, for his testimony is in vain, the judges being unable to rely upon it, viz. (Devarim 19:15): "One witness shall not arise against a man for every transgression and for every sin." Therefore, [if he does so], he is considered a motzi shem ra [the spreader of an evil report], concerning which our Rabbis have said (Sha'arei Teshuvah 22): "One who testified singly against his friend receives stripes of rebellion." And our sages have said (Pesachim 113b): "Three are hated by the Holy One Blessed be He," one of them being "one who sees a thing of ervah [immorality] in his friend and testifies against him singly." But he can reveal the thing secretly to his [the sinner's] Rabbi and to his close confidant, if he knows that his words will be accepted as those of two witnesses. And his Rabbi is permitted to hate him for this and to distance himself from his company, until it becomes known to him that he has repented of his evil way. But his Rabbi may not tell this to others, it being no better than seeing it himself, as we have written above in section 4.

(10) And if one arises and testifies against another by himself before beth-din concerning something forbidden, since no benefit can result from this vis-à-vis monetary [obligations, imposition of] an oath, or invalidation of the other's status of kashruth [halachic fitness] since he is only a single witness in the matter, the only thing he "accomplishes" by this is giving the other a bad name, and he also transgresses the negative commandment of (Devarim 19:15): "One witness shall not testify against a man for every transgression and for every sin," and beth-din must punish him with stripes for this.

R. Akiva Eger takes issue with Kalisher regarding the requirement for supportive evidence for priestly yiḥus. He maintains that the genealogical claims of present-day kohanim are uncorroborated and therefore remain in doubt. Chafetz Chaim (Zevaḥ Todah¹²Zevaḥ Todah is the title of a series of expository notes included by Chafetz Chaim in his Likutei Halakhot (Pietrokow, 5670). The entire work is known by the latter name. Zevaḥim, chap. 13) also shares this view. This position is further elucidated by R. David Friedman, who quotes the exposition by the Sifri, Parshat Shoftim, of the verse, "One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he hath sinned" (Deut. 19:15). The words le-khol avon u-lekhol chat'at are understood by the Sifri as teaching that two witnesses are necessary for both admission to the priesthood and exclusion from performance of the priestly functions.²²R. Levine, Taharat ha-Kodesh, cites Rambam, Hilkhot Parah Adumah 3:4, who states that a total of nine red heifers was offered from the time of Moses until the destruction of the Second Commonwealth and that a tenth will be brought by the Messiah. He concludes that the reason that the red heifer cannot be prepared in our day is because we have no means of ascertaining the genealogical purity of the kohanim. See also R. Shlomoh Kluger, Ḥokhmat Shlomoh, Even ha-Ezer 6:8.