Mishnayos Keilim Perek 14 Mishnah 7

כלי מתכות מיטמאין ומהרין שבורים – metal utensils/vessels that were defiled through [contact with] a corpse and were broken, and he returned and made [new] utensils/vessels on that selfsame day, that they returned to their former [status of] ritual impurity, since he sprinkled [on the third and seventh days ashes from the red heifer mixed in water] upon them while they were whole and they became broken, one does not have to wait until the second sprinkling until the seventh [day], but rather even on one day, he sprinkles twice, one prior to breaking [them] and one after breaking [them] and they are ritually pure immediately. For Rabbi Eliezer holds like Rabban Shimon ben Gamaliel, who said above in Chapter 11 [Mishnah 1] that they didn’t say that the returned to their former [status of] ritual impurity, but rather, only [those] vessels that were defiled through the uncleanness of the soul alone, and the reason for this decree is because of the fence of the waters of the sin-offering as was explained above, therefore, they were not concerned other than that there would be here two [ritual] sprinklings [of the mixture of the water and ashes of the red heifer]. But however, while they are still broken, [ritual] sprinkling is not effective, for sprinkling is not connected with broken [utensils]. But it also requires that the breaking interrupts between each [ritual] sprinkling, because here is an interruption of days between the sprinkling of the third [day] and the sprinkling of the seventh [day]. But they did not want to be stringent in the return of the former ritual defilement which is according to the Rabbis, and they were lenient so that the sprinkling would be effective even that both sprinklings occurred on one day.

ר' יהושע אומר אין הזאה פחות משלישי ושביעי – for they established it like that of the Torah [legislation]. And the Halakha is according to Rabbi Yehoshua.