Sanhedrin 49B

מתני׳ ארבע מיתות נמסרו לבית דין: סקילה, שריפה, הרג, וחנק. רבי שמעון אומר: שריפה, סקילה, חנק, והרג. זו מצות הנסקלין.

Mishnah: 4 types of the death penalty were given over to the court, with which those who committed certain transgressions are executed. They are, in descending order of severity: Stoning, burning, killing by decapitation, and strangulation. R' Shimon says: They are, in descending order of severity: Burning, stoning, strangulation, and killing. This execution, described in the previous chapter, is referring to the mitzva of those who are stoned, i.e., to the process of execution by stoning.

גמ׳ אמר רבא אמר רב סחורא אמר רב הונא: כל מקום ששנו חכמים דרך מניין, אין מוקדם ומאוחר, חוץ משבעה סמנין.

Talmud: Rava says that Rav Seḥora says that Rav Huna says: Wherever A baraita states a halakha by means of a list, there is no significance to the order of their list, except for in the Mishnah that discusses the 7 abrasive substances, where the order is significant.

דתנן: שבעה סמנין מעבירין על הכתם ⁠– רוק תפל, ומי גריסין, ומי רגלים, ונתר, ובורית, קמוליא, ואשלך.

As we learned in a Mishnah (Nidda 61b): One applies 7 abrasive substances to the stain found on a woman’s clothing in order to find out whether the stain is from menstrual blood, and therefore ritually impure, or whether it is another type of stain, and therefore pure. These substances are: Bland spittle, which is the spittle of someone who has not yet tasted anything in the morning; moisture of grits, which is the spittle of one who has chewed the grits of beans; urine; natron; lye [borit]; Kimolian earth [kimuleya]; and potash. If the stain disappears as a result of the application of all of these substances, the stain is considered to have been from blood.

וקתני סיפא: העבירן שלא כסידרן, או שהעבירן שבעתן כאחד ⁠– לא עשה ולא כלום.

And it is taught in the latter clause of that Mishnah that the order of the substances is essential, as it states: If one applied them not in the order prescribed for them, or applied all 7 of them at once, he has done nothing; the laundering has not been effective.