The reason of the difference is, partly because wet seed doth sooner receive and longer retain any pollution; and partly because such seed was not fit to be sown presently; and therefore that necessity which justified the use of the dry seed, which was speedily to be sown, could not be pretended in this case.
Related Commentaries of Leviticus 11:38
Leviticus 11:38
38 But if any water be put upon the seed, and any part of their carcase fall thereon, it shall be unclean unto you.