Sanhedrin1: 3
סְמִיכַת זְקֵנִים וַעֲרִיפַת עֶגְלָה בִּשְׁלשָׁה; דִּבְרֵי רַבִּי שִׁמְעוֹן. וְרַבִּי יְהוּדָה אוֹמֵר: בַּחֲמִשָּׁה. הַחֲלִיצָה וְהַמֵּאוּנִין, בִּשְׁלשָׁה. נֶטַע רְבָעִי וּמַעֲשֵׂר שֵׁנִי שֶׁאֵין דָּמָיו יְדוּעִין, בִּשְׁלשָׁה. הַהֶקְדֵּשׁוֹת בִּשְׁלשָׁה; הָעֲרָכִין הַמִּטַּלְטְלִין בִּשְׁלשָׁה. רַבִּי יְהוּדָה אוֹמֵר: אֶחָד מֵהֶן כֹּהֵן. וְהַקַּרְקָעוֹת תִּשְׁעָה וְכֹהֵן, וְאָדָם כַּיּוֹצֵא בָהֶן.
The semichah of the elders and the decapitation of the calf are by three; [these are] the words of R’ Shimon. R’ Yehudah, however, says: By five. Chalitzah and refusal are before three. The fourth-year fruit and the maaser sheni whose value is unknown are [judged] by three. [Redemption] of articles of hekdesh is [judged] by three. Assessments of movable objects is by three. R’ Yehudah says: One of them [must be] a Kohen. That of real property is by nine and a Kohen, and likewise for a human being.
Sanhedrin1: 4
דִּינֵי נְפָשׁוֹת בְּעֶשְׂרִים וּשְׁלשָׁה. הָרוֹבֵעַ וְהַנִּרְבָּע בְּעֶשְׂרִים וּשְׁלשָׁה, שֶׁנֶּאֱמַר: ,,וְהָרַגְתָּ אֶת־הָאִשָּׁה וְאֶת־הַבְּהֵמָה”, וְאוֹמֵר: ,,וְאֶת־הַבְּהֵמָה תַּהֲרֹגוּ”. שׁוֹר הַנִּסְקָל בְּעֶשְׂרִים וּשְׁלשָׁה, שֶׁנֶּאֱמַר: ,,הַשּׁוֹר יִסָּקֵל וְגַם בְּעָלָיו יוּמָת” — כְּמִיתַת הַבְּעָלִים כָּךְ מִיתַת הַשּׁוֹר.  הַזְּאֵב, וְהָאֲרִי, הַדֹּב, וְהַנָּמֵר, וְהַבַּרְדְּלָס, וְהַנָּחָשׁ מִיתָתָן בְּעֶשְׂרִים וּשְׁלשָׁה. רַבִּי אֱלִיעֶזֶר אוֹמֵר: כָּל הַקּוֹדֵם לְהָרְגָן זָכָה. רַבִּי עֲקִיבָא אוֹמֵר: מִיתָתָן בְּעֶשְׂרִים וּשְׁלשָׁה.
Capital cases are [judged] by twenty-three. The [animal] which commits an act of bestiality or is its recipient [is judged] by twenty-three, as it says: And you shall kill the woman and the animal, and it says: And the animal you shall kill. An ox which is to be stoned [is judged] by twenty-three, as it says: The ox shall be stoned and also its owner shall be put to death —- in the same manner as the owner [is put to] death, the ox is [put to] death.  The wolf, the lion, the bear, the leopard, the bardelas, and the snake are sentenced to death by twenty-three. R’ Eliezer says: Whoever is first to kill them acquires merit. R’ Akiva says: Their death is by twenty-three.