Sifrei Bamidbar 128

(Bamidbar 19:17) "and he shall place upon it living waters": Scripture speaks of spring waters. You say this, but perhaps the intent is "waters which are life to the world" (and all waters are valid)? Though there is no proof (that spring waters are meant), there is support for it in (Bereshit 26:19) "And the servants of Yitzchak dug in the stream and they found there a well of living waters." What is the intent of "and he shall place upon it (the ashes) living waters which are in a vessel"? We are hereby taught that all vessels are equated with earthenware vessels. For it would follow (otherwise), viz.: Since water and earth are consecrated in the instance of sotah (viz. Ibid. 5:12), and water and earth are consecrated in the instance of the (red) heifer, then if I have learned about sotah that all vessels were not equated with earthenware vessels, this should be the case too with the heifer; it is, therefore, written "in a vessel" (unqualified), whereby we are taught that all vessels were equated with earthenware.

(Bamidbar 19:18) "And a clean man shall take": "Taking" is written here, and elsewhere (Ibid. 5) "Just as taking there involves three (objects), so, "taking" here. "hyssop": and not Greek hyssop, and not Kochalith hyssop, and not Roman hyssop, and not desert hyssop — and not any hyssop designated by an epithet.