TT #53 · Parashas Noach · Fourth Aliyah · Passuk 9:6
Whoever sheds the blood of man, by man shall his blood be shed, for in the image of God He made man.
Torah Temimah / classic reading: “by man” = through the agency of a court.
Sefaria — Sanhedrin 56b (Noachide laws)
E-Daf image — Sanhedrin 56b (size=3)
“By man shall his blood be shed” — “by man” means through the agency of man, i.e., through a court of justice.
Custom (requirement of judicial process rather than private vengeance).
Capital punishment for murder must be carried out through a court, not by private blood-vengeance alone.