When Moses drew near to Mount Horeb, he was aware at once that it was a holy place, for he noticed that passing birds did not alight upon it. At his approach the mountain began to move, as though to go forward and meet him, and it settled back into quietude only when his foot rested upon it. The first thing Moses noticed was the wonderful burning bush, the upper part of which was a blazing flame, neither consuming the bush, nor preventing it from bearing blossoms as it burnt, for the celestial fire has three peculiar qualities: it produces blossoms, it does not consume the object around which it plays, and it is black of color. The fire that Moses saw in the bush was the appearance of the angel Michael, who had descended as the forerunner of the Shekinah herself to come down presently. It was the wish of God to hold converse with Moses, who, however, was not inclined to permit any interruption of the work under his charge. Therefore God startled him with the wonderful phenomenon of the burning thorn-bush. That brought Moses to a stop, and then God spoke with him.
There were good reasons for selecting the thorn-bush as the vessel for a Divine vision. It was "clean," for the heathen could not use it to make idols. God's choosing to dwell in the stunted thorn-bush conveyed the knowledge to Moses that He suffers along with Israel. Furthermore, Moses was taught that there is nothing in nature, not even the insignificant thorn-bush, that can exist without the presence of the Shekinah. Besides, the thorn-bush may be taken as the symbol for Israel in several respects. As the thorn- bush is the lowliest of all species of trees, so the condition of Israel in the exile is the lowliest as compared with that of all the other nations, but as the thorn-bush releases no bird that alights upon it without lacerating its wings, so the nations that subjugate Israel will be punished. Also, as a garden hedge is made of the thorn-bush, so Israel forms the hedge for the world, the garden of God, for without Israel the world could not endure. Furthermore, as the thorn- bush bears thorns and roses alike, so Israel has pious and impious members, and as the thorn-bush requires ample water for its growth, so Israel can prosper only through the Torah, the celestial water. And the thorn-bush, the leaf of which consists of five leaflets, was to indicate to Moses that God had resolved to redeem Israel only for the sake of the merits of five pious men, Abraham, Isaac, Jacob, Aaron, and Moses. The numbers represented by the letters composing the Hebrew word for thorn-bush, Seneh, add up to one hundred and twenty, to convey that Moses would reach the age of one hundred and twenty years, and that the Shekinah would rest on Mount Horeb for one hundred and twenty days. Finally, in order to give Moses an illustration of His modesty, God descended from the exalted heavens and spake to him from a lowly thorn-bush instead of the summit of a lofty mountain or the top of a stately cedar tree.