Rashi on Exodus 32:27/רש"י על שמות ל״ב:כ״ז

1כה אמר הי וגו׳ THUS SAITH THE LORD etc. — Where did he say so? In the command, (Exodus 22:19) “He that sacrificeth unto any god shall utterly be destroyed”. Thus is it stated in the Mechilta.

2אחיו HIS BROTHER from the same mother, but from a different father, and who was therefore an ordinary Israelite and not a Levite (Yoma 66b).