Leviticus 11:37

And if any part of their carcase fall in the way upon seed that is to be sown, that which is sown dry shall be clean;

rooted Either this is an adjective with a form similar to that of a participle, or it is an entirely different word and the verse specifies two things. Evidence for the latter is found in “and he gave them vegetables” [Daniel 1:16] where a similar word occurs.

ZERA ZEIRUA’ (SEED OF SOWING). “Zera means ‘seed’ of any kind of seed-plant. Zeirua is the noun (‘sowing,’ ‘thing sown’), like the expression, and let them give us ‘zeiro’im’ (edible seeds) to eat. [And if aught of their carcass fall upon any seed of sowing which is to be sown] it is clean. This is to teach you that food is not fit and susceptible of becoming impure until water has once come upon it.” This is Rashi’s language.
Now Scripture mentioned above, of all the food which may be eaten, that on which water cometh [shall be unclean], establishing the principle that foodstuff must first become susceptible to impurity [through coming into contact with water]. But there the Rabbis interpreted it to mean, on basis of Torath Kohanim. the foodstuff is not rendered impure through the medium of the interior of an [impure] earthen vessel, unless it was made susceptible of receiving impurity by being moistened by water. But here Scripture added that even from [contact with] the creeping things themselves, foodstuff does not become impure unless it was made susceptible [by water]. So it is explained in the Torath Kohanim. 11:8.
It is also possible to say that the expression of all the food which may be eaten. refers to the things mentioned above — meat and various foods. But here He states that even seeds when taken out to be sown, can be rendered impure if they have become susceptible to impurity by being moistened by water. The reason for foodstuffs having to be made susceptible by water [before they can become impure], is that the uncleanness of [dead] creeping things and the other sources of impurity, attaches to foodstuffs in their state of moisteness, but not when they are dry. The Torah then, as an extra precautionary measure, declared impure those foods on which water had once come, although they have [subsequently] become dry, [if they were then touched by any of the sources of impurity], in order that the rule should not vary according to different standards. Now the law of making food susceptible of becoming impure applies also to the impurity [conveyed] by carrion, Scripture having mentioned it here for the reason we have stated above.

אשר יזרע (בקרקע) טהור. Anything still connected to the earth is not subject to ritual defilement.

זרע זרוע, the seed inside seed kernels. The word zerua is the singular mode of the word zeronim, זרעונים in Daniel 1,12, meaning “pulse.” [Alshich explains that it is a reference to raw pulse. At any rate this is the kernel containing the reproductive power of the plant in question. Ed.]