민수기 19:17 할라카: Shulchan Arukh, Yoreh De'ah

All things that if one plants seeds in them they would sprout, they are included in "earth" and one may cover [blood] with them. And if they don't sprout, if they are called "עפר" ("earth") one may cover with them. Therefore, one may cover with dung, and with very fine sand, [fine] enough that the potter doesn't need to crush it at all, and with lime, and with an earthenware shard and brick and barrel stopper of earthenware that was crushed, and with ground stones and ground earthenware shards, and scraps of fine flax, and sawdust, and with food or garments that were burnt until they were made into ash, and with powdered coal, and with stibium, and with millstone dust. But one may not cover with coarse dung, and not with sand that a potter needs to crush, and not with flour and bran-flour, and coarse bran, and not with ground metal if it's not burnt [to ash], except for ground gold which is called "עפר" ("earth"), as it is written "and it has earth of gold". And ash is called "עפר" ("earth"), as it is written "And they should take for the impure from the earth, the burnt [ashes] of the sin-offering".