Leviticus 11:34

all food for eating upon which (such) water cometh shall be unclean, and any fluid which is used for drinking in any such vessel shall be unclean.

drink [Hebrew: mashqeh] a noun; in the phrase “I used to give drink ” [Hebrew: mashqeh] [Nehemiah 1:11] the same word is a verb.

OF ALL THE FOOD WHICH MAY BE EATEN, THAT ON WHICH WATER COMETH, SHALL BE UNCLEAN. Rashi commented: “This verse according to its [Rabbinical] interpretations teaches many things. We learn that food does not become fit to be susceptible of impurity until water has once come upon it, and once water has come upon it, it can subsequently at any time become impure, even after it has become dry, etc. Our Rabbis have further learned from this verse that ‘a secondary impurity’ does not render vessels impure, for so we are taught etc. Again we learn that the coming of water upon vegetation makes it susceptible to impurity only after it has been plucked from the soil etc.” And included among the principles [we learn from this verse], Rashi said: “And we further learn that impure foodstuff does not convey impurity to other objects unless it [the former] consists of at least the size of an egg, for it says, of all the food which may be eaten, which means food which can be eaten in one gulp, and the Sages calculated that the esophagus does not hold more than a hen’s egg.” This is the language of the Rabbi [Rashi.].
But there is [too great a] brevity in Rashi’s comment. For this verse speaks about foodstuff itself becoming impure, and does not refer to its conveying impurity to others. The Rabbi [Rashi], however, derived this principle from what the Rabbis have said in the Torath Kohanim: 9:1. “Of all the food etc. shall be unclean. This teaches that food [upon which a dead creeping thing falls], is rendered impure even if it be of the smallest quantity. Now I might think that it can also convey impurity to other objects if the [original] impure food was of the smallest quantity; Scripture therefore says, which may be eaten. Thus you learn that it cannot render other things impure unless it is itself the size of an egg.” as applying to “impure” food conveying impurity to others, the verse teaching us that the conveyor of the impurity must be of the size which may be eaten, which is, as explained above, the size of an egg. The verse could not refer to the original foodstuff itself becoming impure because of having touched a dead creeping thing [or any “father of impurity” — see above Note 251], for in that case even the smallest quantity of food suffices to be rendered impure. — But, Ramban continues, other scholars have already differed with Rashi on this point, bringing proof etc. (see text). But other authorities have already differed with the Rabbi [Rashi], and they brought proofs that by Scriptural law foodstuffs do not [even] become impure at all unless they are of the size of an egg. Thus the interpretation of the Torath Kohanim [mentioned above] is merely a Scriptural support for a Rabbinic law,, p. 314, Note 449. the Rabbis having added [the stricture] that foodstuffs of even the smallest size also become impure [although they cannot convey impurity to others unless they themselves are the size of an egg]. The main interpretation of the verse is as the Rabbis have said there [in the Torath Kohanim]: 9:1. “The food. This is to exclude food for cattle [that it is not susceptible to impurity]. Of all the food — this is to include food for cattle which one intended to use for human consumption. Which may be eaten, excepting decomposed foods.”

אשר יבא עליו מים יטמא, those who wish to find a reason for G’d’s commandments in order to confound the heretics, and in order to make them intelligible in terms of the laws of nature, would do well to consider this piece of legislation. Foodstuffs, originating in the earth, though subject to ritual impurity under certain conditions, are free from even potential impurity as long as they have not been in contact with water The first step in preparing earth grown food is to wash it, etc. Therefore, as long as no water has fallen on such potential food it is free from such impurity or potential impurity. [Water which fell on it against the wishes of its owner does not count. Ed.]