Exodus 32:20

He took the calf. — To suppress the idolatry, the first step was to destroy the idol. Moses, who must have rallied to his side at once a certain number of the people, laid hold of the calf, and ordered its immediate destruction. He had it submitted to the action of fire, whereby its form was destroyed, and the material, as it would seem, calcined. This calcined material he reduced to a fine powder by rubbing or pounding, and then had the powder sprinkled on the surface of the stream which supplied the camp with water, that so the people might seem, at any rate, to swallow their own sin. Compare the action of Josiah (2 Kings 23:6; 2 Kings 23:12). No doubt, the process of destruction took some time. It is not meant that it was completed, but only that it was commenced, before Moses turned to other matters.