Now Moses kept the flock of Jethro his father in law, the priest of Midian. Exodus 3:1. TDG 321.1
Moses spent forty years as a shepherd of flocks to prepare him to understand himself and to purify himself by emptying himself that the Lord could accomplish His will in him. The Lord did not take for His workmen mere machines in intellect or feelings. Both are essential to do the work, but these human elements of character must be purged from defects, not by talking of the will of God, but by doing His will. “If any man will do his will, he shall know of the doctrine” (John 7:17). Moses was under training to God. He endured a long process of mental training to fit him to be leader of the armies of Israel. TDG 321.2
Inspiration will come to men of God's appointment, but not to any man who retains a high idea of his own mental superiority. For every man whom God will use to do His will must have humble ideas of himself, and must seek in persevering earnestness for light. God will not require any man to become a novice and to sink down into a voluntary humility, and become more and more incapacitated. God calls upon every one with whom He works, to do the very highest kind of thinking and praying and hoping and believing. TDG 321.3
Many have, as had Moses, very much to unlearn in order to learn the very lessons that they need to learn. He had need to be self-trained by severest mental and moral discipline, and God wrought with him before he could be fitted to train others in mind and heart. He had been instructed in the Egyptian courts. Nothing was left as unnecessary to train him to become a general of armies. The false theories of the idolatrous Egyptians had been instilled into his mind, and the influences surrounding him and things his eyes looked upon could not be easily shaken off or corrected. Thus it is with many who have had a false training in any line. All the idolatrous rubbish of heathen lore must be removed, bit by bit, item by item, from Moses’ mind. Jethro helped him in many things to a correct faith, as far as he himself understood. He was working upward toward the light, when he could see God in singleness of heart.... TDG 321.4
God has done everything for us. What have we done? Shall we become faithful stewards of His grace?—Manuscript 45, November 8, 1890, “At Sands [now Stanley], Virginia,” diary. TDG 321.5