Quotation על במדבר 15:43

And from where one is called one, it is said, "How shall one thousand come after them?" And from where the Holy One, blessed be He, is called one, And where the Torah is called one, as it is said, "One Torah will be yours." I am the head of all the commandments and the top of all the letters:...

Blessed [is His] Name, Whose glorious kingdom is forever and ever.²Jacob wished to reveal to his sons the ‘end of the days,׳ whereupon the Shechinah departed from him. Said he, “Perhaps, Heaven forbid! there is one unfit among my children.” His sons exclaimed to him, “Hear Israel” etc., just as there is only One in your heart so is there only One in our heart. Ben Lakish explained that Jacob said, “Blessed [is His] Name” in response to his sons’ exclamation. The Sages wondered, “Shall we recite it aloud when our teacher Moses did not say it? Shall we not say it at all, when Jacob ordained it?” Thus, the Rabbis enacted that it be said quietly.—Maseches Pesachim 56a.
When Moses went up to the heavens, he heard the angels praise God by saying, “Blessed [is His] Name, etc.” When he returned to earth, he taught it to the Jewish People. We say it in an undertone so as not to offend the angels. On Yom Kippur however, when we are considered like angels, we are permitted to say ברוך שם aloud.—Midrash Rabba to Deuteronomy

(Bamidbar 15:22) "And if you err and do not do all of these mitzvoth": Idolatry was in the category of all the mitzvoth for (unwitting transgression of) which the congregation (i.e., beth-din) brings a bullock (viz. Vayikra 4:14), and Scripture here removed it from its category (for special mention), that the congregation bring a bullock for a burnt-offering and a he-goat for a sin-offering, for which reason this section was stated. "And if you err and do not do all of these mitzvoth": Scripture here speaks of idolatry. You say idolatry, but perhaps (it speaks of his transgressing) all of the mitzvoth of the Torah. It is, therefore, (to negate this) written (Ibid. 24) "And it shall be, if by the eyes of the congregation it were done in error" — Scripture hereby singles out one mitzvah. And which is that? (the injunction against) idolatry. You say it is idolatry, but perhaps it is (any) one of all the mitzvoth stated in the Torah. It is, therefore, written "And if you err and do not do all of these mitzvoth": This comes to define "the one mitzvah." Just as one who transgresses all of the mitzvoth divests himself of the Yoke, and breaks the covenant, and perverts the Torah, so, he who transgresses one mitzvah does the same, as it is written (Devarim 17:2-3) "to destroy His covenant (— turning to the worship of other gods.") And "the covenant" is nothing other than Torah, as it is written (Ibid. 28:69) "These are the words of the covenant, etc." Rebbi says "all" is written here (Bamidbar 15:22), and "all" is written elsewhere, (Devarim 5:8) "all likenesses." Just as "all" there speaks of idolatry, so, "all" here. (Bamidbar, Ibid.) "which the L-rd spoke to Moses": Whence is it derived that one who acknowledges idolatry denies the ten commandments? It is written (here, in respect to idolatry) "which the L-rd spoke to Moses," and there, (in respect to the ten commandments, Shemot 20:1) "And G-d spoke all these words, saying." (Psalms 62:12) "One thing has G-d spoken; (two things ['I am the L-rd your G-d, etc.' and 'There shall not be unto you other gods, etc.'] have I heard.") (Jeremiah 23:29) "Is My word not like fire, says the L-rd (and like a hammer shattering rock?") Whence do I derive (the same, i.e., that one who acknowledges idolatry denies [not only what we heard from G-d,]) but also what Moses was commanded (and relayed to us)? From (Ibid. 23) "All that the L-rd commanded you by the hand of Moses." And whence do I derive (the same for) what was commanded to the forefathers? From (Ibid.) "from the day that the L-rd commanded." And from when did the L-rd begin to command? From Adam, viz. (Bereshit 2:15) "And the L-rd G-d commanded the man, etc." And whence do I derive (the same for) what was commanded to the prophets? From (Ibid.) "and onwards throughout your generations." We are hereby apprised that one who acknowledges idolatry denies the ten commandments, and what was commanded to Moses, and what was commanded to the forefathers, and what was commanded to the prophets. And one who denies idolatry acknowledges the entire Torah.