When Moses descended from Mount Sinai and saw the idol-worship of the Israelites, he cried 'Who is on the Lord's side?' This question is still relevant for all men today.
Exod.32.25-26And when Moses saw that the people were naked; (for Aaron had made them naked unto their shame among their enemies:) Then Moses stood in the gate of the camp, and said, Who is on the LORD'S side? let him come unto me. And all the sons of Levi gathered themselves together unto him.