Midrash sur La Genèse 49:3

Why did he say to them Gather yourselves together, assemble yourselves (Gen. 49:1–2)? He did so to let them realize that they would be exiled twice. After he had designated the elders among them, he began to rebuke them, saying: Reuben, thou art my firstborn (Gen. 49:3). From that very moment Israel merited reciting the Shema. Why? When Jacob was about to depart from this world, he reflected upon it and said: “My grandfather Abraham begot Isaac and Ishmael, and my father, Isaac, begot me and Esau; perhaps there is a blemish in my family.” When they heard this, they proclaimed in unison: Hear, O Israel, the Lord our God, the Lord is one (Deut. 6:4). Hence it is written: Hearken to Israel, thy father (Gen. 49:2).

Reuben, thou art My firstborn, My might and the first fruits of My strength; the excellency of dignity, and the excellency of power. unstable as water, have not thou the excellency (Gen. 49:3–4). Thou art my firstborn. You are my firstborn, the product of the first drop of semen I produced in eighty years.¹⁴Cf. Genesis Rabbah 98:4, “in eighty-four years.” In fact, I did not even experience nocturnal pollution before then. My firstborn. Are you like me? The excellency of dignity, and the excellency of power. Three crowns were available to you: priesthood, kingship, and the right of the firstborn. The excellency of dignity alludes to the priesthood, as is said: And Aaron lifted up his hands (Lev. 9:22); the excellency of power refers to kingship, as it is said: And he will give power unto his king (I Sam. 2:10); the birthright is indicated by the double portion he received, as is said: By giving him a double portion (Deut. 21:17). But you have lost them all. Why? Because you are as unstable as water, and therefore have not thou the excellency.

(Gen. 49:3:) REUBEN, YOU ARE MY FIRST-BORN. One said < it was > to his discredit, and another said < it was > to his credit. To his discredit: He said to him: REUBEN, YOU ARE MY FIRST-BORN.⁴⁷Gen. R. 98(99):4. You are a first-born, and I am a firstborn.⁴⁸By virtue of having bought Esau’s birthright. R. Judah b. R. Shallum said: For eighty-four years Jacob never saw a < nocturnal > pollution.⁴⁹Gen. R. 97, New Version, on 49:3 (= p. 1204 in the Theodor-Albeck edition); cf. Gen. R. 99 (another version):6 (= p. 1277 in the Theodor-Albeck edition); Tanh., Gen. 12:9; see also Gen. R. 68:5; Meg. 17a and Rashi, ad loc. I am a first-born, and you are a first-born.⁵⁰Gen. R. 98(99):4 explains that Reuben did not follow his father’s example, but (according to Gen. 35:22, 49:4) slept with his father’s concubine and thereby lost his birthright, his priesthood, and his right to kingship. See also below; Targum Pseudo-Jonathan, Gen. 49:3; Tanh., Gen. 12:9.