Reference for Parah 6:3
הַמְקַדֵּשׁ בַּשֹּׁקֶת וְהַטְּפִי בְתוֹכָהּ, אַף עַל פִּי שֶׁפִּיו צַר כָּל שֶׁהוּא, הַמַּיִם שֶׁבְּתוֹכוֹ מְקֻדָּשִׁין. אִם הָיָה סְפוֹג, הַמַּיִם שֶׁבְּתוֹכוֹ פְסוּלִים. כֵּיצַד יַעֲשֶׂה, יְזַלֵּף עַד שֶׁהוּא מַגִּיעַ לַסְּפוֹג. נָגַע בַּסְּפוֹג, אַף עַל פִּי שֶׁהַמַּיִם צָפִין עַל גַּבָּיו כָּל שֶׁהֵן, פְּסוּלִין:
One who sanctifies in a trough, and a <i>tefi</i> [a vessel with a very narrow opening] is inside it, even if the opening [of the <i>tefi</i>] is a [very small] width, the water inside it is sanctified. If there was a sponge [in the trough when the ashes were added], the water inside it is invalid [since the water is not contained in a vessel]. What should he do? He empties [the vessel] until he reaches the sponge [and the collected water is valid]. [But] if he touches the sponge, even if the water is floating above it in any amount, it [the water] is invalid [since invalid water left the sponge and mixed with the valid water].