Israel was now encamped, and this vast army was just entering upon action, which was likely to keep them together for a long time, and therefore it was fit to give them particular directions for the good ordering of their camp. And the charge is in one word to be clean. They must take care to keep their camp pure from moral, ceremonial, and natural pollution.

I.From moral pollution (Deu 23:9): When the host goes forth against thy enemy then look upon thyself as in a special manner engaged to keep thyself from every evil thing. 1. The soldiers themselves must take heed of sin, for sin takes off the edge of valour; guilt makes men cowards. Those that put their lives in their hands are concerned to make and keep their peace with God, and preserve a conscience void of offence; then may they look death in the face without terror. Soldiers, in executing their commission, must keep themselves from gratifying the lusts of malice, covetousness, or uncleanness, for these are wicked things - must keep themselves from the idols, or accursed things, they found in the camps they plundered. 2. Even those that tarried at home, the body of the people, and every particular person, must at that time especially keep from every wicked thing, lest by sin they provoke God to withdraw his presence from the host, and give victory to the enemy for the correcting of his own people. Times of war should be times of reformation, else how can we expect God should hear and answer our prayers for success? Psa 66:18. See Sa1 7:3.

II.From ceremonial pollution, which might befal a person when unconscious of it, for which he was bound to wash his flesh in water, and look upon himself as unclean until the evening, Lev 15:16. A soldier, notwithstanding the constant service and duty he had to do in the camp, must be so far from looking upon himself as discharged from the observance of this ceremony that more was required from him than at another time; had he been at his own house, he needed only to wash his flesh, but, being in the army, he must go abroad out of the camp, as one concerned to keep it pure and ashamed of his own impurity, and not return till after sunset, Deu 23:10, Deu 23:11. By this trouble and reproach, which even involuntary pollutions exposed men to, they were taught to keep up a very great dread of all fleshly lusts. It were well if military men would consider this.

III.From natural pollution; the camp of the Lord must have nothing offensive in it, Deu 23:12-14. It is strange that the divine law, or at least the solemn order and direction of Moses, should extend to a thing of this nature; but the design of it was to teach them, 1. Modesty and decorum; nature itself teaches them thus to distinguish themselves from beasts that know no shame. 2. Cleanliness, and, though not niceness, yet neatness, even in their camp. Filthiness is offensive to the senses God has endued us with, prejudicial to the health, a wrong to the comfort of human life, and an evidence of a careless slothful temper of mind. 3. Purity from the pollutions of sin; if there must be this care taken to preserve the body clean and sweet, much more should we be solicitous to keep the mind so. 4. A reverence of the divine majesty. This is the reason here given: For the Lord thy God walketh by his ark, the special token of his presence, in the midst of thy camp; with respect to that external symbol this external purity is required, which (though not insisted on in the letter when that reason ceases) teaches us to preserve inward purity of soul, in consideration of the eye of God, which is always upon us. By this expression of respect to the presence of God among them, they were taught both to fortify themselves against sin and to encourage themselves against their enemies with the consideration of that presence. 5. A regard one to another. The filthiness of one is noisome to many; this law of cleanliness therefore teaches us not to do that which will be justly offensive to our brethren and grieve them. It is a law against nuisances.

Thou shalt have also a place without the camp,.... A place prepared, as the Targums of Onkelos and Jonathan, provided on purpose for the use hereafter suggested; so Ben Melech:

whither thou shalt go forth abroad; to do the necessities of nature, which they were to do without the camp, not in any place they thought fit and most convenient, but what was appointed for that purpose.

When the host goeth forth against thine enemies, then keep thee from every wicked thing--from the excesses incident to camp life, as well as from habits of personal neglect and impurity.