Shevuot 3A

ועל הזקן שתים מיכן ושתים מיכן ואחת מלמטה;

And for marring the edges of his beard there are two edges from here, on one side of his face, and two from there, on the other side, and one from below.

חדא דמיחייב עלה תרתי; תנא שבועות שתים שהן ארבע.

The Talmud explains: As apparent from the Mishnah in Makkot, this is a case where there is one prohibition for which one is liable to receive two punishments. Continuing on this theme, the tanna taught in the beginning of tractate Shevuot examples of other sets of halakhot that can be formulated similarly, beginning with: With regard to oaths on an utterance, there are two types that are actually 4 types.

מאי שנא הכא דתני להו לכולהו, ומאי שנא גבי יציאות שבת ומראות נגעים, דלא קתני להו לכולהו?

The Talmud inquires: What is different here, in tractate Shevuot, that the Mishnah teaches all the sets of halakhot that can be formulated as: Two that are 4, and what is different with regard to the chapter beginning: The acts of carrying out that are prohibited on Shabbat, i.e., the first chapter of tractate Shabbat, and the chapter beginning: And the shades of leprous marks, i.e., the first chapter of tractate Nega’im, where the Mishnah does not teach all of them, rather only the specific set of halakhot relevant to that tractate?

אמרי: שבועות וידיעות הטומאה דגבי הדדי כתיבן, ודמיין אהדדי בקרבן עולה ויורד ⁠– תני להו גבי הדדי; ואיידי דתנא תרתי ⁠– תנא כולהו.

The rabbis say in explanation: Since the passages of oaths and of liability based on one’s awareness of the defiling of the Temple or its sacrificial foods are written together in the Torah (see Leviticus 5:2–4), and they are also similar to each other in that they can both incur liability to bring a sliding-scale offering, the Mishnah therefore taught both of them together here. And once it already taught two sets, it continued and taught all of them.