מדרש על בראשית 15:4

7...

Another interpretation: "As these nations that you are about to dispossess, etc. but you not like this to you" (Deuteronomy 18:14). It is speaking about Avraham, as he saw through astrology that the constellation said to him that Avram and Sarai would not have a child. What did the Holy One, blessed be He, do for them? Rabbi Yehudah beRabbi Simon said in the name of Rabbi Chanin, "It is written (Genesis 15:5), 'And He took him outside and said, "Observe towards the heavens."' He raised him above the dome of the firmament (above the skies)." As "out" can only [indicate] firmament, as it is stated (Proverbs 8:26), "Before He had made the land and the outside places." And it is also stated (Isaiah 33:7), "Behold the [angels of] Ariel yelled outward." The Holy One, blessed be He, said to him, "That which you said (Genesis 15:3), 'Behold, the one over my household shall inherit me'; the matter is not like this, 'but rather the one who will come out of your innards will inherit you' (Genesis 15:4)." He said [back] to Him, "Are You telling me that I will have a child?" The Holy One, blessed be He, said to him, "Leave your measure! Avram will not have a child, Avraham will have a child; Sarai will not have a child, Sarah will have a child." "And He took him outside." He said to him, "Behold, you are above the constellation. Who is greater than whom? Is it not you, as you are above it?" "Observe towards the heavens." It is not written, "Lift up your eyes towards the heavens," here, but rather "observe." [This] is like a man who observes [what is] below from above. So is it stated (Psalms 13:4), "Observe; answer me, Lord, my God." "And He said to him, 'So will be your seed'" (Genesis 15:5). Moshe said to them, "Just as Avraham left the constellation and did not occupy himself with it, also you." "The Lord, your God, did not give you like this" (Deuteronomy 18:14).

Rabbi Simeon said: Our father Abraham wrote (in his will and bequeathed) all that he had as an inheritance to Isaac, as it is said, "And Abraham gave all that he had unto Isaac" (Gen. 25:5). He took the document and gave it into the hands of Eliezer, his servant, (who) said, Since the document is in my hand all his money is in my hand, so that he might go and be recommended (thereby) in his father's house and with his family.