John Gill Bible Commentary

But if any water be put upon the seed,.... Either accidentally or on purpose; whether on sowing seed, and with water with which they water the field, as Aben Ezra interprets it; or on seed used for food, by steeping it in water, as sometimes wheat is, and boiled; and whether it is water or the rest of the liquors, and whether they are put on the seed, or the seed falls into them, it matters not, as Jarchi says: and any part of their carcass fall thereon; that is, on the seed, though Aben Ezra observes, some say upon the water: the Targum of Jonathan adds, in its moisture, or while it is wet; and so may be thought to be more susceptible of impurity from the touch of a dead reptile, or any part of it, and which would render it unfit for sowing or eating, until it was dried and cleansed; yea, Jarchi says, if it falls thereon, even after it is dried: it shall be unclean unto you; unfit for use.