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 Sanhedrin (conclusion of the discussion of “echad”).
מאי אחד – אחד אחד, מכאן לעדות מיוחדת שהיא פסולה.
English: What is meant by “one”? One-and-one — from here [we learn] that disjoint testimony is invalid [for capital cases].
This unit consolidates the ruling that the two witnesses must form a single, simultaneous unit of observation and testimony; any separation renders the testimony “miyuchedet” and therefore invalid for the death penalty.
Derash on the verse (Bavli) — not a formal named middah of the 13. The word “echad” is read as a technical term excluding sequential or spatially separated testimony.
Capital cases require two witnesses who observed the act together as one unit; testimony given “one by one” does not combine to produce a death sentence.