Талмуд к Кетубот 11:2

MISHNAH: By the words of two witnesses or three witnesses shall a death sentence be imposed⁴¹Deut. 19:15. Criminal sentences can be imposed only on the basis of oral testimony, not of circumstantial evidence.. If testimony is confirmed by two, why did the verse mention three? Only to compare three to two. Since three may prove that two are plotters, two also may prove that three are plotters. And from where even a hundred? The verse says “witnesses”⁴²The repetition, two witnesses or three witnesses, when it could have been “two or three witnesses”, implies that any number of witnesses have the same status as do two..
Rebbi Simeon says, since two are executed only if both are plotters, so three are executed only if all three are plotters. And from where even a hundred? The verse says “witnesses”⁴²The repetition, two witnesses or three witnesses, when it could have been “two or three witnesses”, implies that any number of witnesses have the same status as do two..
Rebbi Aqiba says, the third is only mentioned to punish him harshly and to identify his judgment with that of the others. If the verse in this way punished the accessory of criminals like criminals⁴³Since the third witness is not essential for proof in court., so much more it will reward the accessory to one who keeps the commandments as one who keeps the commandments.
Since the testimony of two [witnesses] is invalid if one of them is found to be a relative or a disqualified person⁵¹If one witness is disqualified by the rules of Mishnah Sanhedrin either 3:6 or 3:7, there is only one testimony, insufficient by biblical standards., the same holds for three if one of them is found to be a relative or a disqualified person. From where even for a hundred? The verse says⁴²The repetition, two witnesses or three witnesses, when it could have been “two or three witnesses”, implies that any number of witnesses have the same status as do two., witnesses.
Rebbi Yose said, when has this been said? In criminal trials, but in civil trials the testimony should be upheld by the remaining [witnesses]⁵²Since Deut. 19:19 is formulated for criminal trials, the argument that any number of witnesses have the same status as two witnesses is not necessarily true for civil trials. In money matters, any two qualified witnesses can testify. For example, it is admissible that marriage contracts be signed first by two qualified witnesses and after them by any number of family members of both sides (cf. Gittin 8:12, Note 105).. Rebbi says, both in criminal and in civil trials, if they warned them⁵³If in a criminal case a disqualified person or two related persons both warned the perpetrator not to engage in criminal behavior, their action makes them witnesses and all witnesses have to be disqualified under the argument of Mishnah 12. But if they were eye witnesses but not those who delivered the warning, they are not forced to testify; the trial may proceed without them.. But if they did not warn them, what should two brothers do who were eye-witnesses to a murder?