III. They were commanded to sanctify themselves, that they might be prepared to attend the ark; and with good reason: For to-morrow the Lord will do wonders among you, v. 5. See how magnificently he speaks of God's works: he doeth wonders, and is therefore to be adored, admired, and trusted in. See how intimately acquainted Joshua was with the divine counsels: he could tell before-hand what god would do, and when. See what preparation we must make to receive the discoveries of God's glory and the communications of his grace: we must sanctify ourselves. This we must do when we are to attend the ark, and God by it is about to do wonders among us; we must separate ourselves from all other cares, devote ourselves to God's honour, and cleanse ourselves from all filthiness of flesh and spirit. The people of Israel were now entering into the holy land, and therefore must sanctify themselves. God was about to give them uncommon instances of his favour, which by meditation and prayer they must compose their minds to a very careful observation of, that they might give God the glory, and take to themselves the comfort, of these appearances.