Before his death, Jacob gathered his sons in order to take his leave from them and to convey his final words to each of them. The Sages add that on that occasion, Jacob also sought to assess his sons’ faith, and he was overjoyed when he saw they were all steadfast in their faith.

From here, Israel [i.e., the Jewish people] received the recitation of Shema. When Jacob our patriarch was passing from the world, he summoned his twelve sons. He said to them: Is the God of Israel in the heavens your Father? Do you believe that the Holy One, blessed be He, is divided, that there is more than one god? The sons said to him: Hear us, Israel [i.e., Jacob] our father: Just as you believe there is no division within the Holy One, blessed be He, so too we believe there is no division. Rather: The Lord is our God, the Lord is one. Jacob then pronounced: Blessed be the name of His glorious kingdom forever and ever. Rabbi Berekhya and Rabbi Helbo said in the name of Rabbi Shmuel: This explains why the Jewish people come early every morning and late every evening, every day, and recite: Hear Israel, our father from the Cave of Makhpela: The same matter that you commanded us is still practiced among us: The Lord is our God, the Lord is one. (Bereshit Rabba [Theodor-Albeck] 98)