Moses, therefore, tells us that, since God had forbidden them to pass the borders of Edom, they went by another way; but immediately afterwards he adds, that they basely rebelled, without being provoked to do so by any new cause. They had before been rebellious under the pressure of hunger or thirst, or some other inconvenience; but now, when there were no grounds for doing so, they malignantly exasperate themselves against God.
–John Calvin commenting on Numbers 21, the Old Testament lesson for today; this was quoted by yours truly in the Sermon this morning