9:7-29 That the Israelites might have no pretence to think that God brought them to Canaan for their righteousness, Moses shows what a miracle of mercy it was, that they had not been destroyed in the wilderness. It is good for us often to remember against ourselves, with sorrow and shame, our former sins; that we may see how much we are indebted to free grace, and may humbly own that we never merited any thing but wrath and the curse at God's hand. For so strong is our propensity to pride, that it will creep in under one pretence or another. We are ready to fancy that our righteousness has got for us the special favour of the Lord, though in reality our wickedness is more plain than our weakness. But when the secret history of every man's life shall be brought forth at the day of judgment, all the world will be proved guilty before God. At present, One pleads for us before the mercy-seat, who not only fasted, but died upon the cross for our sins; through whom we may approach, though self-condemned sinners, and beseech for undeserved mercy and for eternal life, as the gift of God in Him. Let us refer all the victory, all the glory, and all the praise, to Him who alone bringeth salvation.
21. I cast the dust thereof into the brook that descended out of the mount—that is, "the smitten rock" (El Leja) which was probably contiguous to, or a part of, Sinai. It is too seldom borne in mind that though the Israelites were supplied with water from this rock when they were stationed at Rephidim (Wady Feiran), there is nothing in the Scripture narrative which should lead us to suppose that the rock was in the immediate neighborhood of that place (see on Ex 17:5). The water on this smitten rock was probably the brook that descended from the mount. The water may have flowed at the distance of many miles from the rock, as the winter torrents do now through the wadies of Arabia-Petræa (Ps 78:15, 16). And the rock may have been smitten at such a height, and at a spot bearing such a relation to the Sinaitic valleys, as to furnish in this way supplies of water to the Israelites during the journey from Horeb by the way of mount Seir and Kadesh-barnea (De 1:1, 2). On this supposition new light is, perhaps, cast on the figurative language of the apostle, when he speaks of "the rock following" the Israelites (1Co 10:4) [Wilson, Land of the Bible].