In Numb. viii. 18, 19, the subject of redemption is again touched, and the additions are significant. Now the service of the Levites "in the tent of meeting" is by way of atonement for the children of Israel, "that there be no plague among the children of Israel when the children of Israel come nigh unto the sanctuary." Atonement is not with blood in this case, but by the service of the living substitute. While the general scope of the Mosaic law requires the shedding of blood in order that the claim of God may be met, this exception must not be forgotten. And in a sense it is the chief instance of atonement, far transcending in expressiveness those in which animals were slaughtered for propitiation. The whole congregation, threatened with plagues and disasters in approaching God, has protection through the holy service of the Levitical tribe. Here is substitution of a kind which makes a striking point in the symbolism of the Old Testament in its relation to the New. The principle may be seen in patriarchal history. The ten in Sodom, if ten righteous men could have been found, would have saved it, would have been its atonement in a sense, not by their death on its behalf but by their life. And Moses himself, standing alone between God and Israel, prevails by his pleading and saves the nation from its doom. So our Lord says of His disciples, "Ye are the salt of the earth." Their holy devotion preserves the mass from moral corruption and spiritual death. Again, "for the elect's sake," the days of tribulation shall be shortened (Matt. xxiv. 22).