Parashas Masei · Passuk 35:30 · TT note 3
Chabad.org — English translation + Rashi
Torah Temimah points to Sanhedrin 33b (TT note on “וְעֵד אֶחָד לֹא יַעֲנֶה”).
E-Daf — Sanhedrin 33b · Sefaria
English: “A single witness shall not answer” — he shall not answer either for acquittal or for conviction.
A lone witness may neither convict nor acquit in a capital case.
In capital matters a single witness is barred from any testimony that would affect the verdict, whether for guilt or innocence.