Parah, Chapter 7, Mishnah 8. This chapter teaches that one who is engaged in drawing the water for the chatas, sanctifying it with the ashes, or sprinkling it, may not turn aside to any outside labor. An act that serves the sacred work is part of the mitzvah; an act that does not serve it is a melachah, and a melachah in the middle of the process leaves the water pasul. Our mishnah presents two cases where the deciding factor is not what a person did, but what he had in mind while doing it.
Setting the jar aside, and turning it over to dry
The first half of the mishnah opens with "hamatznia es hachavis", a person who stows his jar away in a sheltered spot, and the reason is given as "shelo tishaver", in order that the vessel not be smashed. The mishnah then offers a second version of the same case: "o shekfa'ah al piha", or that he inverted the jar onto its rim, with the purpose stated as "al menas lenagva", meaning that it should dry out. From here the halachah divides according to what stood in his mind. If his purpose was "lemalos bo", to use that jar for further drawing from the well, the verdict is "kasher", and the water he has already drawn retains its fitness. But if his purpose was "leholich ba es hakiddush", to have a vessel ready for transporting water that has already been mixed with the ashes, the verdict is "pasul", and the water is ruined.
The picture is this. A person has filled his jar from the well and poured its contents into the trough where the kiddush, the mixing with the ashes, will be performed. Now he has an empty jar on his hands. He might set it in a protected place so that it should not get smashed. Or he might upend it, letting the last of the water run out, and leave it resting on its mouth so that it should dry quickly.
If his intent was to keep the jar ready for further drawing, so that he can bring up more water for the sanctification, his act belongs to the drawing itself, and the water he has drawn remains fit. But if his intent was to have the jar ready to transport the water once it has already been mixed with the ashes, then the act he performed did nothing at all for the drawing. It is an outside labor, and the water he collected is pasul.
Clearing the sherds out of the trough
The mishnah's second ruling opens with "hamefaneh charasin", one who removes fragments of pottery, "mitoch hashoket", out of the trough. Should his motive be "bishvil shetachazik mayim harbeh", namely that the trough be able to contain a greater volume of water, the ruling is "ksheirin", the water remains fit. The mishnah then adds the contrasting case, "v'im bishvil", and if his reason was rather "shelo yehu ma'akvin oso", that the fragments not delay and hinder him, "b'sha'ah shehu zolef es hamayim", at the moment when he comes to pour the water out, then the ruling is "pasul", the water is disqualified.
Here too the setting is the interval between the drawing of the water and its sanctification. Sherds have collected in the trough and are taking up room. If a person removes them so that the trough will be able to hold a greater quantity of chatas water, his act serves the drawing, it is no melachah, and the water stays fit.
But if he removes them for the sake of the stage that comes afterward, so that nothing should obstruct him when he comes to pour out the water and sprinkle it, the picture changes. He is thinking of the sprinkling: some of the water in the trough has been sanctified and he wishes to sprinkle it. Others explain the case as pouring the water off from the trough into another vessel. Either way, clearing the sherds contributed nothing to the drawing of the water, and so it stands as an outside labor and the water becomes unfit.
Both halves of the mishnah teach the same striking point. Two people may perform an identical act in the identical place at the identical moment, and for one the water remains fit while for the other it is spoiled. Everything hangs on whether the act was in the service of the work at hand.