Verse 21. Shall wash his clothes - Because he is unclean. It is strange, that the same water should cleanse one person, and defile another. But God would have it so, to teach us that it did not cleanse by any virtue in itself, or in the work done, but only by virtue of God's appointment: to mind the laws of the imperfection of their priesthood, and their ritual purifications and expiations, and consequently of the necessity of a better priest and sacrifice and way of purifying; and to shew that the efficacy of God's ordinances doth not depend upon the person or quality of his ministers, because the same person who, was polluted himself could and did cleanse others. He that toucheth the water - Either by sprinkling of it, or by being sprinkled with it; for even he that was cleansed by it, was not fully cleansed as soon as he was sprinkled, but only at the even of that day.
Verse 22. The unclean person - Not he who is so only by touching the water of separation, ver. 21, but he who is so by the greater sort of uncleanness, which lasted seven days, and which was not removed without the use of this water of purification.