LXX Num 19:9

καὶ συνάξει ἄνθρωπος καθαρὸς τὴν σποδὸν τῆς δαμάλεως καὶ ἀποθήσει ἔξω τῆς παρεμβολῆς εἰς τόπον καθαρόν. καὶ ἔσται τῇ συναγωγῇ υἱῶν Ἰσραὴλ εἰς διατήρησιν· ὕδωρ ῥαντισμοῦ, ἅγνισμά ἐστιν.

Then a man who is ceremonially clean is to gather up the ashes of the heifer and store them in a ceremonially clean place outside the camp. They must be kept by the congregation of Israel for preparing the water of purification; this is for purification from sin.