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.

21. he that sprinkleth … ; and he that toucheth the water of separation shall be unclean until even—The opposite effects ascribed to the water of separation—of cleansing one person and defiling another—are very singular, and not capable of very satisfactory explanation. One important lesson, however, was thus taught, that its purifying efficacy was not inherent in itself, but arose from the divine appointment, as in other ordinances of religion, which are effectual means of salvation, not from any virtue in them, or in him that administers them, but solely through the grace of God communicated thereby.