Parashas Eikev · Passuk 9:21
As for that sinful thing you had made, the calf, I took it and put it to the fire; I broke it to bits and ground it thoroughly until it was fine as dust, and I threw its dust into the brook that comes down from the mountain.
Torah Temimah points to Avodah Zarah 54a.
TT lemma: ואכת אתו (unit 2 of 2).
English: “And I crushed it” — this teaches that the destruction of an idol is by grinding and scattering to the wind, or casting into the sea. Into a sea where ships pass, crushing is required lest travelers find it; into the Dead Sea, where ships do not pass, crushing is not required. This verse — casting into the wadi — implies the need to crush first.
Custom (how to destroy an idol)
Proper biur of avodah zarah is pulverizing and dispersing; the method depends on whether recovery is plausible.