עַל־פִּ֣י שְׁנַ֣יִם עֵדִ֗ים א֛וֹ שְׁלֹשָׁ֥ה עֵדִ֖ים יוּמַ֣ת הַמֵּ֑ת לֹ֣א יוּמַ֔ת עַל־פִּ֖י עֵ֥ד אֶחָֽד׃
A person shall be put to death only on the testimony of two or more witnesses; no one shall be put to death on the testimony of a single witness.—
Torah Temimah points to Sifrei Devarim.
אין לי אלא אם מת כסדר הזה, מניין לרבות שאר המומתים, ת״ל על פי שנים עדים או שלשה עדים יומת המת.
English: I know only [the requirement of two witnesses] when he dies according to this procedure [stoning]; from where do I include all other forms of capital punishment? From the verse “on the testimony of two witnesses or three witnesses shall the dead be put to death.”
The general language “shall the dead be put to death” extends the two-witness requirement to every form of capital execution, not only the stoning described in this chapter.
Derash on the verse (Sifrei) — not a formal named middah of the 13. The broad phrasing is taken as an inclusion of all four methods of capital punishment.
Every form of capital punishment — stoning, burning, beheading, and strangulation — requires the testimony of two witnesses.