When we recite the Shema in our davening, we do something very strange. We interrupt Deuteronomy chapter 6 with a phrase that does not appear anywhere in the Tanakh. (Closest thing is Psalm 72:19). There are two different midrashim that help us to understand this puzzling practice.
I. Bavli, Pesachim 56a: First our gemara cites a Tosefta (Pesachim 3:19 in Lieberman edition, see Dr. Shamma Friendman's Tosefta Atikta Siman 18) –
Our Rabbis have taught, "How did they (the people of Jericho) used to korchin(fold over) the Shema? They would say Hear O Israel, The Lord is our God, the Lord in oneand they would not pause, these are the words of R. Meir. R. Yehuda says, they would pause but they would not say Barukh shem… (Blessed is the name of his glorious kingdom for all eternity."
Whatever the people of Jericho were in fact doing it was something that rabbis were not happy with. Presumably both R. Meir and R. Yehuda take for granted the recitation of Barukh Shem… The gemara then asks –
And we, why do we recite it (barukh shem)? As R. Shimon b. Lakish taught, "And Yaakov called to his children and said gather and I will tell you (what will be with you at the end of days – the gemara does not quote the entire verse, Genesis 49:1) – Yaakov wanted to reveal the end of days to his sons and the divine presence left him. He said [to himself], 'Perhaps, heaven forfend, there is amongst my progeny one who is invalid – like Abraham from whom came forth Ishmael and like Issak from whom came forth Essav.' His sons said to him, 'Hear O Israel, the Lord id our God, the Lord is one!' They said, 'Just as there is none other in your, there is no other in our heart.' At that moment Yaakov opened his mouth and said, 'Barukh Shem…'"
The Rabbis said, "How shall we act? Shall we say it (barukh shem)? Moshe did not say it! Shall we skip it? Yaakov did say it! The instituted that it should be recited quietly…"
R. Avahu said, "They instituted that it should be said out loud because of the heretics." But in Nehardea, where there were no heretics, they still say it quietly. (See also Devarim Rabbah, ed. Vilna 3:35, ed. Lieberman pgs. 67-68)
This is the source that I was raised on.
1. How did Yaakov's sons call him by his first name? (We are not going to address this issue.)
2. How does this source account for our custom on Yom Kippur to say barukh shem out loud? For that we need another midrash.
II. Midrash Dvarim Rabbah (ed. Vilna 3:36, ed. Lieberman s.v chavivah kriyat shema, pg. 68). I am going to quote (excerpt) from the Lieberman edition:
The reading of Shema is so beloved that it was given to the Jewish People who give praise first, and then the angels. The Jewish People say The Lord is our God, the Lord is one and then the angels say barukh shem…And why do the Jewish people say it quietly?…So said Moshe to the Jewish people, 'All of the mitzvot that I give you I received from the Torah. But this recitation I heard in from the angels and I stole it from them. Therefore, you should say it quietly…And why do they say it out loud on Yom Kippur? Because they are like angels.
This Midrash is sited by the Tur in Orach Chayyim 691 as the explicit source for our custom. See also Magen Avraham691:8 for an anlysis of this issue. (Chochmat Shlomo on Orach Chayyim 61 also deals with this problem.
It is always a challenge to find the rabbinic source upon which our contemporary practice is based. This treasure hunt is just one of the aspects that I love in the world of Talmud Torah.