Deuteronomy 9:21

And I took your sin, the calf which ye had made
Which was the object of their sin, which lay in making and worshipping it; see ( Isaiah 31:7 )

and burnt it with fire, and stamped it;
with his feet after it was burnt, to bring it into small pieces:

and ground it very small;
or, as the Targum of Jonathan,

``ground it in a mortar well;''

the burnt and broken pieces:

even until it was as small as dust;
being ground to powder, as in ( Exodus 32:20 )

and I cast the dust thereof into the brook that descended out of the
mount;
and made the children of Israel to drink of it, as in the previously mentioned place; (See Gill on Exodus 32:2); all this was done before the prayer for Aaron and the people.