פירוש על פרה 7:8

המצניע את החבית – that he draws water with it to put in the trough, and after he emptied [the water] from it, he put it away/hid it prior to mixing the water [with the ashes] in the trough, this putting away [of the bucket] is not considered work, because he still needs it to fill it up [with water], and it is the need of drawing/filling water. And similarly, he inverted/bent it over on its mouth also to dry it because he still wants to fill [water] in it, it is not considered work, and it is fit/appropriate for filling/drawing. But, if he did so to bring the mixed ashes and water, that is, the water that is mixed [with ashes], since it is not for the purpose of filling/drawing water, it is considered work and the filling/drawing [of water] is invalid.

One who puts the jar away in order that it shall not be broken, or if he inverted it in order to dry it, [If he did one of these things] so that he might draw more water with it, [the water he had already drawn] is valid; But if he intended to carry in it the ashes, it is invalid. There are two actions described here, each that can invalidate the water if they were done with a certain intention, but won't invalidate the water if done with another intention. The actions are both done for the sake of the jar either to protect it or to dry it and they are both done between the emptying of the water into a trough and the mixing of the water with the ashes. If he did one of these things with the intention to draw more water for the same mixture, then this is not "work" done in between filling and mixing and the water remains valid for use. However, if he is protecting or drying the jar to use it for any other purpose, even a purpose connected to the mixing of the ashes, such as carrying in it the ashes, the water is invalid.

בשביל שתחזיק מים הרבה – this emptying is not considered work.

One who cleared potsherds from a trough: If in order that it may hold more water, the water is valid; But if he intended that they should not hinder him when he pours out the water, it is invalid. The idea of this section is similar to that above. Someone clears potsherds from the trough into which he has put the water to use it for mixing the ashes. If he clears them in order to make more room in the trough, the water is valid. However, if he is removing them because he doesn't want them to bother him when he pours the mixture from the trough into a flask (from which he will sprinkle) then this action counts as work and it invalidates the mixture. Again, although this is done for the sake of the mixture, it still invalidates it.

בשעה שהוא זולף -when he sprinkles.

פסול – this emptying out is considered work.