Devibhagavatapurana 11.14.44

11.14.44

kṛtamapyakṛtaṃ satyaṃ bhasmasnānaṃ vinā mune |
bhasmasnānaṃ śrutiproktamāgneyaṃ snānamucyate ||

All the religious actions performed without this ash bath seem as if no actions are done at all. This ash bath is stated in the Vedas. Its another name is the Fire Bath. By this ash bath both outside and inside are purified. So a man who uses ashes gets the entire fruit of worshipping S’iva. By the water Bath only the outside dirt is removed; but by this bath of ashes, outside dirts and inside dirts, both are fully removed. If this water bath be taken many times daily, still without an ash bath, one’s heart is not purified. What more shall I speak of the greatness of ashes, the Vedas only appreciate its glories rightly! Yea, very rightly!