When Jethro bestowed his daughter Zipporah upon Moses as his wife, he said to his future son-in-law: "I know that thy father Jacob took his wives, the daughters of Laban, and went away with them against their father's will. Now take an oath that thou wilt not do the same unto me," and Moses swore not to leave him without his consent, and he remained with Jethro, who made him the shepherd of his flocks. By the way he tended the sheep, God saw his fitness to be the shepherd of His people, for God never gives an exalted office to a man until He has tested him in little things. Thus Moses and David were tried as shepherds of flocks, and only after they had proved their ability as such, He gave them dominion over men.
Moses watched over the flocks with loving care. He led the young animals to pasture first, that they might have the tender, juicy grass for their food; the somewhat older animals he led forth next, and allowed them to graze off the herbs suitable for them; and finally came the vigorous ones that had attained their full growth, and to them he gave the hard grass that was left, which the others could not eat, but which afforded good food for them. Then spake God, "He that understandeth how to pasture sheep, providing for each what is good for it, he shall pasture My people."
Once a kid escaped from the flock, and when Moses followed it, he saw how it stopped at all the water courses, and he said to it: "Poor kid, I knew not that thou wast thirsty, and wast running after water! Thou art weary, I ween," and he carried it back to the herd on his shoulder. Then said God: "Thou hast compassion with a flock belonging to a man of flesh and blood! As thou livest, thou shalt pasture Israel, My flock."
Not only did Moses take heed that no harm should come to the herds under his charge, but he was also careful that they cause no injury to men. He always chose an open meadow as his pasturing place, to prevent his sheep from grazing in private estates.
Jethro had no reason to be dissatisfied with the services rendered to him by his son-in-law. During the forty years Moses acted as his shepherd not one sheep was attacked by wild beasts, and the herds multiplied to an incredible degree. Once he drove the sheep about in the desert for forty days, without finding a pasturing place for them. Nevertheless he did not lose a single sheep.
Moses' longing for the desert was irresistible. His prophetic spirit caused him to foresee that his own greatness and the greatness of Israel would manifest themselves there. In the desert God's wonders would appear, though it would be at the same time the grave of the human herd to be entrusted to him in the future, and also his own last resting- place. Thus he had a presentiment at the very beginning of his career that the desert would be the scene of his activity, which not only came true in the present order of things, but also will be true in the latter days, when he will appear in the desert again, to lead into the promised land the generation, arisen from their graves, that he brought forth from Egyptian bondage.
Wandering through the desert, he reached Mount Horeb, which is called by six names, each conveying one of its distinctions. It is "the mountain of God," wherein the Lord revealed His law; "Basban," for God "came there"; "a mountain of humps," for the Lord declared all the other mountains unfit for the revelation, as "crookbackt" animals are declared unfit for sacrifices; "mountain of abode," because it is the mountain that God desired for His "abode"; Sinai, because the "hatred" of God against the heathen began at the time when Israel received the law thereon; and Horeb, "sword," because there the sword of the law was drawn upon the sinners.