Parashas Masei · Passuk 35:30 · TT note 5
Chabad.org — English translation + Rashi
Torah Temimah points to Sanhedrin 34a (TT note on “לֹא יַעֲנֶה בְנֶפֶשׁ לָמוּת”).
E-Daf — Sanhedrin 34a · Sefaria
English: It was taught: From where [do we know] that if one of the students said “I have something to say against him” they do not listen to him? From “a single [witness] shall not answer concerning a person to put to death.”
Students may not introduce arguments for conviction once deliberation has begun.
The verse bars not only a lone witness but also a single disciple from speaking to convict; the court hears only the established testimony and the judges’ own deliberation.