Rashi on Leviticus 11:37/רש"י על ויקרא י״א:ל״ז

1זרע זרוע means seed of any kind of seed-plant. The word זרוע is a noun (not a passive participle, when it would be punctuated ‎זָרוע), like (Daniel 1:12) "and let them give us of pulse — זֵרוֹעִים".

2טהור הוא HE SHALL BE CLEAN — Scripture by means of this and the following verse teaches you that it does not become fitted and proper to be termed food and therefore to be receptive of uncleanness, until water comes upon it.