Jamieson, Fausset and Brown on Exodus 32:26-28

26-28. Moses stood in the gate of the camp, and said--The camp is supposed to have been protected by a rampart after the attack of the Amalekites.

Who is on the Lord's side? let him come unto me--The zeal and courage of Moses was astonishing, considering he opposed an intoxicated mob. The people were separated into two divisions, and those who were the boldest and most obstinate in vindicating their idolatry were put to death, while the rest, who withdrew in shame or sorrow, were spared.