This is the law, when a man dieth in a tent: all that come into the tent, and all that is in the tent, shall be unclean seven days.

Jamieson-Fausset-Brown Bible Commentary

14. when a man dieth in a tent, &c.-The instances adduced appear very minute and trivial; but important ends, both of a religious and of a sanitary nature, were promoted by carrying the idea of pollution from contact with dead bodies to so great an extent. While it would effectually prevent that Egyptianized race of Israelites imitating the superstitious custom of the Egyptians, who kept in their houses the mummied remains of their ancestors, it ensured a speedy interment to all, thus not only keeping burial places at a distance, but removing from the habitations of the living the corpses of persons who died from infectious disorders, and from the open field the unburied remains of strangers and foreigners who fell in battle.

Matthew Henry's Concise Commentary

19:11-22 Why did the law make a corpse a defiling thing? Because death is the wages of sin, which entered into the world by it, and reigns by the power of it. The law could not conquer death, nor abolish it, as the gospel does, by bringing life and immortality to light, and so introducing a better hope. As the ashes of the heifer signified the merit of Christ, so the running water signified the power and grace of the blessed Spirit, who is compared to rivers of living water; and it is by his work that the righteousness of Christ is applied to us for our cleansing. Those who promise themselves benefit by the righteousness of Christ, while they submit not to the grace and influence of the Holy Spirit, do but deceive themselves; we cannot be purified by the ashes, otherwise than in the running water. What use could there be in these appointments, if they do not refer to the doctrines concerning the sacrifice of Christ? But comparing them with the New Testament, the knowledge to be got from them is evident. The true state of fallen man is shown in these institutions. Here we learn the defiling nature of sin, and are warned to avoid evil communications.