Mishnayos Parah Perek 7 Mishnah 4

קדש לי ואקדש לך – as for example, that each one filled water for himself, and this one came and mixed [with ashes] the water of that one, and that one mixed the water [with ashes] of this one, the one who mixed [the water with ashes] first what he mixed for his fellow is kosher/fit, for his fellow did not do any work other than until after his waters were mixed [with ashes], but when they (i.e., the waters) were mixed with ashes, no work/labor invalidates it. But what the second [person] who mixed [ashes in the water] for the first [person] is invalid, for the first invalidated in that he mixed [water and ashes] in the water of the second ‘person] before his waters were mixed [with ashes].

מלא לי ואמלא לך – the latter drawing of water/filling is kosher/fit, but the first drawing of water/filling is invalid, that is, that the waters that were filled were invalidated through the work of filling/drawing that he filled for his fellow.

קדש לי ואמלא לך – that he had the waters filled/drawn and said to his fellow, “mix for me my waters [with ashes] and afterwards, I will draw [water] for you.”

שניהם כשרים – for the work/labor does not invalidate after the mixing [of ashes with water]. And this also when the waters were drawn/filled for him, his waters are fit/kosher, that from when the waters were filled/drawn for him, he did not do any work.

מלא לי ואקדש לך – that the other that had waters filled/drawn and he said to him: “Fill for me [waters] first, and afterwards I will mix [the ashes in the water] for you.”

שניהם פסולים – this one who filled until his waters were not mixed [with ashes], and this one who mixed [ashes with water] for his fellow from when his waters were filled up/drawn.