Torah Temimah cites Toras Kohanim.
“Asham asham to Hashem” — this is the midrash that Yehoiada the Kohen expounded: whatever comes on account of chatas or asham, olot are purchased with it.
Diyuk of doubled “asham asham” — surplus funds become public olot.
Leftover asham funds become public olot rather than remaining private asham animals. The doubled language is the scriptural basis for Yehoiada’s ruling that surplus from chatas and asham dedications is used to purchase burnt offerings for the public altar.