Parashas Shemos · Passuk 2:12
Chabad.org — English translation + Rashi
Torah Temimah points to Sanhedrin 58b (verified).
Sefaria — Exodus 2:12
Sefaria — Sanhedrin 58b
E-Daf — Sanhedrin 58b
English: “And he struck the Egyptian” — R’ Chanina said: An Egyptian who struck an Israelite is liable to death, as it is said, “And he turned this way and that and saw that there was no man, and he struck the Egyptian.”
On the daf / in context: See the cited source for the full section.
Custom
Chazal teach that the Egyptian who was beating a Hebrew had already incurred the death penalty; Moshe acted as an agent of justice.