There has been much debate as to what we are to understand by the leprosy in the garment or in a house. Was it an affection identical in nature with the leprosy of the body? or was it merely so called from a certain external similarity to that plague?
However extraordinary the former supposition might once have seemed, in the present state of medical science we are at least able to say that there is nothing inconceivable in it. We have abundant experimental evidence that a large number of diseases, and, not improbably, leprosy among them, are caused by minute parasitic forms of vegetable life; and, also, that in many cases these forms of life may, and do, exist and multiply in various other suitable media besides the fluids and tissues of the human body. If, as is quite likely, leprosy be caused by some such parasitic life in the human body, it is then evidently possible that such parasites, under favourable conditions of heat, moisture, etc., should exist and propagate themselves, as in other analogous cases, outside the body; as, for instance, in cloth, or leather, or in the plaster of a house; in which case it is plain that such garments or household implements, or such dwellings, as might be thus infected, would be certainly unwholesome, and presumably capable of communicating the leprosy to the human subject. But we have not yet sufficient scientific observation to settle the question whether this is really so; we can, however, safely say that, in any case, the description which is here given indicates a growth in the affected garment or house of some kind of mould or mildew; which, as we know, is a form of life produced under conditions which always imply an unwholesome state of the article or house in which it appears. We also know that if such growths be allowed to go on unchecked, they involve more or less rapid processes of decomposition in that which is affected. Thus, even from a merely natural point of view, one can see the high wisdom of the Divine King of Israel in ordering that, in all such cases, the man whose garment or house was thus affected should at once notify the priest, who was to come and decide whether the appearance was of a noxious and unclean kind or not, and then take action accordingly.
Whether the suspicious spot were in a house or in some article it contained, the article or house (the latter having been previously emptied) was first shut up for seven days (xiii. 50; xiv. 38). If in the garment or other article affected it was found then to have spread, it was without any further ceremony to be burnt (xiii. 51, 52). If it had not spread, it was to be washed and shut up seven days more, at the end of which time, even though it had not spread, if the greenish or reddish colour remained unchanged, it was still to be adjudged unclean, and to be burned (xiii. 55). If, on the other hand, the colour had somewhat "dimmed," the part affected was to be cut out; when, if it spread no further, it was to be washed a second time, and be pronounced clean (xiii. 58). If, however, after the excision of the affected part, the spot appeared again, the article, without further delay, was to be burned (xiii. 57).
The law, in the case of the appearing of a leprosy in a house (xiv. 33-53), was much more elaborate. As in the former case, when the occupant of the house suspects, "as it were a plague in the house," he is to go and tell the priest; who is, first of all, to order the emptying of the house before he goes in, lest that which is in the house, should it prove to be the plague, be made unclean (ver. 36). The diagnosis reminds us of that of the leprosy in the body; greenish or reddish streaks, in appearance "lower than the wall," _i.e._, deep-seated (ver. 37). Where this is observed, the empty house is to be shut up for seven days (ver. 38); and at the end of that time, if the spot has spread, "the stones in which the plague is" are to be taken out, the plaster scraped off the walls of the house, and all carried out into an unclean place outside of the city, and new stones and new plaster put in the place of the old (vv. 40-42). If, after this, the plague yet reappear, the house is to be adjudged unclean, and is to be wholly torn down, and all the material carried into an unclean place without the city (vv. 44, 45). If, on the other hand, after this renewal of the interior of the house, the spots do not reappear, the priest "shall pronounce the house clean, because the plague is healed" (ver. 48). But, unlike the case of the leprous garment, this does not end the ceremonial. It is ordered that the priest shall take to cleanse (_lit._ "to purge the house from sin") (ver. 49) two birds, scarlet, cedar, and hyssop, which are then used precisely as in the case of the purgation of the leprous man; and at the end, "he shall let go the living bird out of the city into the open field: so shall he make atonement for the house: and it shall be clean" (vv. 50-53).