Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
In chapter 6 we find the principles on which the conquests of Israel are founded. The work is altogether God's. He may indeed exercise His people in conflict, but it is He who does all. "They went up every man straight before him." There is submission here in the use of means, readiness to follow a course which, in the eyes of the world, is absurd and without object; but which loudly proclaims the presence of the Lord in the midst of His people. There is entire dependence upon God, a perfect confidence in Him, which openly declares it has nothing else to do but to obey Him. The promise is sure; they act in obedience. That is the principle Joshua-type of the energy and the mind of the Spirit in one who enjoys communion with the Lord-is certain of success; and in this assurance of faith he acts without hesitation. In effect, all the strength of the enemy falls to the ground without the use of any means that could account for it. Another principle is, that there must be no fellowship whatever with that which constitutes the power of the enemy of God, with the world, and that which is its strength. All is accursed. It is so with us in this world. If the world of Sodom had enriched Abraham, he would have been dependent on that world; he would have owed it something; he would not have been at liberty from it to belong entirely to God. "And ye in any wise keep yourselves from the accursed thing, lest ye make yourselves accursed." God may use these things by consecrating them to Himself, if He will. But if man, if the Christian, meddle with them, the Lord must judge him. cities walled up to heaven, the greatest obstacles are as nothing; how can they be with God? But holiness, complete separation from the world because power is of God-that is the condition of strength. Jericho, representing the enemy's power and means of defence (inasmuch as it was the first city standing as a barrier to arrest the progress of God's people), is put under a curse for ever; and sentence is passed against any one who should rebuild it (see Kg1 16:34). The abstract principles of the power of God and the enemy's strength are presented by this city and its fall, in what evidences them, and in contrast. But, if God is there, and the world is utterly condemned, His grace calls out from this world a people saved by faith from its abominations, and Rahab, a poor unworthy sinner, is saved from its judgment, and has her place and part with the people of God [See Note #1].
It is noticeable that she, like Ruth, the stranger, is in the line of the Lord's royal genealogy (Mat 1:5).