A clue to its date is to be found in its conception of cleanness. The idea found in the Prophets and the New Testament that moral wrongdoing renders unclean must be based upon some earlier conception, namely, upon the Old Testament conception of ritual uncleanness. Now ritual uncleanness was originally physical uncleanness only; the idea of moral right or wrong did not enter into it at all: this is perfectly clear from the whole contents of
Le 11-15. On the other hand we find the idea of moral cleanness and uncleanness fully formed in the Psalms, Proverbs, and in the Prophets, including the earlier prophets, Amos, Hosea, and Isaiah. In H (the Law of Holiness,
Le 17-26) we find an intermediate conception. We find that whereas in
Le 11-15 sexual acts which were lawful rendered unclean equally with those which were unlawful, in H, adultery
and incest are denounced as rendering specially unclean, the idea being that their technical uncleanness became more intensely unclean through their immorality (
Le 18:24-30). Similarly, converse with familiar spirits and wizards, which probably involved physical defilement (perhaps through the ingredients used in charms), is mentioned as specially causing defilement, probably as such technical defilement would be intensified by the unlawfulness of dealing with familiar spirits and wizards at all (
Le 19:31). Sins, however, which did not in themselves entail physical uncleanness, such e.g. as injustice, are not mentioned in H as rendering unclean, though they are so regarded in the Prophets. First, then, we have ritual uncleanness, which is physical only in the rules of
Le 11-15 (Mosaic rules undoubtedly embodying a pre-Mosaic
conception); lastly, we have moral wrong in itself rendering unclean, in the Psalms and the Prophets; intermediately we have the transitional conception in H. The date therefore of the Law of Holiness may be Mosaic, but must be considerably earlier than the earliest of the writing prophets.