Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Num 5:1-10) The unclean to be removed out of the camp, Restitution to be made for trespasses.
(v. 11-31) The trial of jealousy.
The camp was to be cleansed. The purity of the church must be kept as carefully as the peace and order of it. Every polluted Israelite must be separated. The wisdom from above is first pure, then peaceable. The greater profession of religion any house or family makes, the more they are obliged to put away iniquity far from them. If a man overreach or defraud his brother in any matter, it is a trespass against the Lord, who strictly charges and commands us to do justly. What is to be done when a man's awakened conscience charges him with guilt of this kind, though done long ago? He must confess his sin, confess it to God, confess it to his neighbour, and take shame to himself; though it go against him to own himself in a lie, yet he must do it. Satisfaction must be made for the offence done to God, as well as for the loss sustained by the neighbour; restitution in that case is not enough without faith and repentance. While that which is wrongly gotten is knowingly kept, the guilt remains on the conscience, and is not done away by sacrifice or offering, prayers or tears; for it is the same act of sin persisted in. This is the doctrine of right reason, and of the word of God. It detects hypocrites, and directs the tender conscience to proper conduct, which, springing from faith in Christ, will make way for inward peace.
This law would make the women of Israel watch against giving cause for suspicion. On the other hand, it would hinder the cruel treatment such suspicions might occasion. It would also hinder the guilty from escaping, and the innocent from coming under just suspicion. When no proof could be brought, the wife was called on to make this solemn appeal to a heart-searching God. No woman, if she were guilty, could say "Amen" to the adjuration, and drink the water after it, unless she disbelieved the truth of God, or defied his justice. The water is called the bitter water, because it caused the curse. Thus sin is called an evil and a bitter thing. Let all that meddle with forbidden pleasures, know that they will be bitterness in the latter end. From the whole learn, 1. Secret sins are known to God, and sometimes are strangely brought to light in this life; and that there is a day coming when God will, by Christ, judge the secrets of men according to the gospel, Rom 2:16. 2. In particular, whoremongers and adulterers God will surely judge. Though we have not now the waters of jealousy, yet we have God's word, which ought to be as great a terror. Sensual lusts will end in bitterness. 3. God will manifest the innocency of the innocent. The same providence is for good to some, and for hurt to others. And it will answer the purposes which God intends.