Mikvaos, Chapter 4, Mishnah 1. This chapter turns to one of the central subjects of the entire maseches: mayim she'uvim, drawn water. We have already seen that a mikveh which has not yet reached its full measure of forty se'ah of rainwater is ruined if three lugin of mayim she'uvim fall into it. What exactly gives water the status of she'uvim is the theme that the coming mishnayos will unfold.
One point, however, is already established: water becomes drawn water only when it has been received inside a keli, a vessel that has a beis kibul, a hollow receiving area designed to hold water or to hold something else. The question our mishnah addresses is what happens when water collects in such a vessel, but not because the owner wanted it filled.
Every Sort of Vessel
The mishnah opens: "Hamani'ach keilim tachas hatzinor," one who sets vessels beneath the drainpipe. Picture a man who does not want the runoff from his roof spreading over his courtyard, so he stands a pail, a bucket or a pot under the spout to catch it. At that moment his purpose could not be clearer: he wants that vessel to fill.
The mishnah then stresses how broad this halachah is. "Echad keilim gedolim," whether the vessels are enormous. In the laws of tumah we learn that a vessel whose receptacle holds more than forty se'ah is not mekabel tumah, it cannot become tamei. That leniency belongs to Hilchos Tumah alone; for mayim she'uvim, size is irrelevant, and water gathered in such a huge vessel is fully drawn water.
"Ve'echad keilim ketanim," and whether the vessels are tiny. A receptacle too small to contain even enough oil to smear on the smallest limb of a newborn is not reckoned a keli at all for the purposes of tumah. For she'uvim, it is a keli.
"Afilu k'lei galalim, k'lei avanim," and even vessels shaped out of animal dung or hewn from stone, "k'lei adamah," or formed of ordinary earth. Not one of these materials is mekabel tumah. Yet because every one of them contains a hollow that holds liquid, the mishnah teaches "poslin es hamikveh": whatever water gathers inside them is drawn water and ruins the mikveh.
Placing and Forgetting
At this point the mishnah presents its machlokes: "echad hamani'ach ve'echad hashoche'ach," both the man who set the vessel down and the man who left it forgotten. What is the case of forgetting? He stood the pail under the spout intending to catch the runoff, the sky stayed dry, and the vessel slipped from his mind entirely. A fortnight went by, rain finally fell, and the pail filled on its own.
Beis Shammai holds that the water is she'uvim. His original placement was made lada'as, with full intent, and that intent was never revoked. Time passed and he stopped thinking about the vessel, but forgetfulness alone does not undo what he set out to do, and the water collected there is drawn water "kedivrei Beis Shammai."
"U'Veis Hillel metaharin beshoche'ach." Beis Hillel rules that when he forgot about the vessel and only afterward it filled, the water is not she'uvim. Once the matter slipped from his mind, the original intent was unsettled, and no fresh intent replaced it. The vessel is therefore regarded as "nismaleh shelo lada'as," filled without intention.
Rebbi Meir and Rebbi Yosi
Rebbi Meir relates that the matter went further: "nimnu," the talmidim of the two schools were counted, those of Beis Shammai maintaining that the forgotten vessel's water is she'uvim against those of Beis Hillel who held it is not. When the count was tallied, "rabu Beis Shammai," the Shammai side proved the more numerous. By force of that majority the halachah in the case of forgetting is that the water counts as drawn and renders the mikveh invalid.
Rebbi Meir adds a second ruling: "umodim," Beis Shammai concedes "beshoche'ach bachatzer," where the vessel was forgotten out in the open courtyard rather than directly under the spout. When a man positions a pail beneath the drainpipe, his aim is written all over the arrangement, and his later forgetfulness cannot uproot that original kavanah. But a vessel standing in the middle of the yard with no pipe above it never displayed any intent to gather water at all. In such a case "shehu tahor," the water that collected in it does not become she'uvim, and it remains fit water for a mikveh.
Here it is worth recalling what we learned earlier: there are prescribed ways to draw off and remove water from a vessel so that it does not turn into she'uvim afterward.
Rebbi Yosi rejects Rebbi Meir's report altogether. As he sees it, no counting ever took place; instead, "adayin machlokes bimekomah omedes," the argument remains unresolved and no majority was ever produced. It follows that a vessel forgotten beneath the spout is judged according to Beis Hillel and its water is valid, following the general principle in any such unresolved machlokes between the two schools.