Mishnayos Sanhedrin Perek 1 Mishnah 2

מכות – forty stripes

בשלשה – as it is written (Deuteronomy 25:1): “…and they go to law, and a decision is rendered.” The word ושפטום/and they go to law – [denotes] two, and there can never be an even-balanced court, so we add upon them another [judge], for we have three [judges].

רבי ישמעאל אומר: בעשרים ושלשה – it comes [by a comparison of the word] רשע רשע –[found in two different places by analogy]. It is written here (Deuteronomy 25:1) “declared the one in the right and the other in the wrong”, and it is written there (Numbers 35:31): “[You may not accept a ransom for the life of a murderer] who is guilty of capital crime; [he must be put to death].”Just as there (i.e., in Numbers 35:31), with twenty-three [judges], so here (Deuteronomy 25:1) with twenty-three [judges].

עיבור החודש – the Sanctification of the [New] Month, and since it was necessary [for the Mishnah] to teach the intercalation of the year (i.e., proclaiming a leap-year/inserting a second Adar), so too it taught the intercalation of a month (i.e., proclaiming a month just past one of thirty days).

בשלשה מתחילין – to see if one is able to appoint a Jewish court on this. And if one of the three [judges] says that there is a need for the Jewish court to sit and investigate if it is necessary to intercalate the year because of the solstice, and the spring and the fruition, but two say that it is not necessary, for there is no doubt here and for sure it is not necessary to have a leap year, the individual is nullified in his minority [status]. Two [judges] who say to appoint a Jewish court and one [judge] says not to appoint [a Jewish court], we follow after the two [judges], and we add two other [judges] who will engage in give-and-take in the matter, and hence we have here five. If two [judges] say that we must intercalate [the year] and three [judges] say that it is not necessary, the two are nullified in their minority. [But if] two [judges] say that it is not necessary and three [judges] say that it is necessary, we follow after the majority, and add another two [judges] so that that there will be seven and we intercalate it [i.e., the year]. And the Gemara explains that these three, five and seven correspond to the Priestly Blessing, for there are three words in the first verse, and in the second, five [words] and in the third [verse] seven [words], and the Halakah is according to Rabban Shimon ben Gamaliel.