Numbers 19:15

And every open vessel
An earthen one, as the Targum of Jonathan; and so Jarchi interprets it; and Maimonides ^F18 observes, that this is only to be understood of an earthen vessel:

which hath no covering bound upon it;
a linen or a woollen cloth wrapped and tied about it:

[is] unclean;
the air of the house getting into it by its being uncovered.

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FOOTNOTES:

F18 In Misn. Cholin, c. 1. sect. 6.