Thought from Today's Old Testament Passage: Then God spoke to Israel in the visions of the night, and said, "Jacob, Jacob!" And he said, "Here I am." So He said, "I am God, the God of your father; do not fear to go down to Egypt, for I will make of you a great nation there. "I will go down with you to Egypt, and I will also surely bring you up again; and Joseph will put his hand on your eyes." (Gen. 46:2-4)
Moses tells us expressly that Jacob did not offer sacrifices to idols, but to the God of Isaac, the only true God, who was also the God of Abraham, Shem, and Noah. It was He who had promised to the patriarchs the Seed of the Woman, who was to bruise the head of the serpent and bring salvation to all men. But here we may ask why Jacob offered sacrifices at Beer-sheba while he was on the way to Egypt. He indeed had been invited by Pharaoh and his son Joseph to come to Egypt in order to save himself and his family from starvation. But the thought might have occurred to him whether that really was the will of God who had promised him and his descendants the land of Canaan as his inheritance. He did not want to undertake anything without God's command, merely upon the invitation of Pharaoh and Joseph. For him indeed it was a most serious matter to leave Canaan, the land of promise, where his fathers Abraham and Isaac had lived and died, and to go into a strange country which was far away from the land of promise. He therefore asked God at Beer-sheba to reveal to him His will in this matter.
Nor did God let him ask in vain, for He revealed to Jacob in a vision at night that he was to go into Egypt without fear, since He would be with him and there make him a great nation. God also added the promise that He would bring him up again from Egypt and that Joseph was to put his hand upon his eyes. From this we learn that God is not a fickle Being who lies or changes His promises, but He is faithful in all things He says and does.
J. Theodore Mueller, trans, Luther's Commentary on Genesis, Vol. II, (Grand Rapids: Zondervan Publishing House, 1958), p. 325