Makhshirin, Chapter One, Mishnah Five
1) If one shook a bundle of vegetables and [water] dropped down from the upper [side] to the lower [side]:
a) Bet Shammai say: this comes under the law of if water be put.
b) But Bet Hillel say: this does not come under the law of if water be put.
2) Bet Hillel said to Bet Shammai: if one shakes a stalk, do we fear lest water drops from one leaf on the other leaf?
a) Bet Shammai said to them: a stalk is only one, but a bundle has many stalks.
3) Bet Hillel said to them: behold, if one lifted a sack full of produce and put it beside the river, do we fear lest water drops from the upper [side] to the lower [side]?
4) But if he lifted two sacks and placed them one upon the other, the lower [sack] comes under the law of if water be put.
a) Rabbi Yose says: the lower [sack] remains insusceptible to uncleanness.
Section one: According to Bet Shammai, even if the water only moves from part of the bundle to another part, it still causes the water to make the produce susceptible to impurity. In contrast, Bet Hillel again rules leniently. Since the water has not left the bundle, it does not yet cause produce to be susceptible.
Section two: Bet Hillel argues with Bet Shammai from what they perceive to be an analogous case. If one has a stalk of some sort of produce and one shakes it and water drops from one leaf to another, all agree that the water has not yet been separated from its source such that it causes susceptibility to impurity. So too, if one shakes a bunch of produce it does not yet cause susceptibility.
Bet Shammai says that the two situations are different, for when it comes to the stalk, it is only one piece of produce. The bundle contains many pieces of produce, and therefore we can perceive of the water as having left its original place and moving to another.
Section three: Bet Hillel again argues against Bet Shammai. When one brings a sack of produce to the river so that water will soak out of the sack and flow into the river, we do not consider the produce to be susceptible because water flowed from the upper side of the bag to the lower side. So too, in the case of a bunch of produce, even if water flows from one part to the other, it is not susceptible.
Section four: However, Bet Hillel agrees that if the water flows from one sack to the other, that it does cause the lower sack to be susceptible to impurity.
Rabbi Yose says that even in this case the water does not cause susceptibility because it has not yet been separated from its totality.