Musar su Genesi 15:4

Abraham expressed the fear that his slave Eliezer would inherit him (Genesis 15,2). G–d told him: "Not this one will inherit you, but someone who is your very own issue will inherit you" (15,3). The message was that a different servant, i.e. Israel My servant will inherit you.

All these matters are alluded to in the word הזה in Genesis 28,17. Bereshit Rabbah 63,8, commenting on Genesis 25,22, where Rebeccah complained about the fetuses within her quarreling, by saying: אם כן למה זה אנכי, quotes Rabbi Nechemiah as saying that Rebeccah had sufficient merit to become the mother of twelve tribes, in accordance with the numerical value of the letters in the word זה; seven corresponding to the letter ז, and five to correspond to the letter ה. Did Rabbi Nechemyah think that we could not count to twelve and had to have this calculation broken down for us? I believe the Midrash wanted to stress why the number twelve here is composed of a combination of 7+5, and not of, say, 8+4 or 9+3. Why did the Midrash have to see in that number a reference to the twelve tribes? The Torah does not mention anything about that number of children! Maybe the number twelve refers to something else?