And Said (Spoke)
Vayomer Hashem el Moshe lemor
And Hashem said to Moshe saying:Daber el-benei Yisarel v'amarta aleihem v'asu lahem tzitzit al kanfei vigdeihem l'dorotam
Speak to the Children of Yisrael and say to them that they are to make themselves tzitzit on the corners of their garments, throughout their generations.Venat'nu al tzitzit hakanaf petil techelet
And they are to place upon the tzitzit of each corner a thread of techelet.V'haya lachem l'tzitzit ur-item oto uz-chartem et kol mitzvot Hashem va-asitem otam
And it shall constitute tzitzit for you, that you may see it and remember all the commandments of Hashem and perform them;Velo taturu acharei l'vavchem v'acharei aineichem, asher-atem zonim achareihem
And not explore after your heart and after your eyes after which you stray.Lemaan tizk'ru va-asitem et kol mitzvotai vih-yitem kedoshim l'Elokeichem
So that you may remember and perform all My commandments; and be holy to your G-d.Ani Hashem Elokeichem asher hotzeiti etchem mei-eretz Mitzrayim lih-yot lachem l'Elokim ani Hashem Elokeichem. Emet
I am Hashem, your G-d, Who has removed you from the land of Egypt to be a G-d to you; I am Hashem your G-d. It is true.
This passage of the Shema' is from BaMidbar 15:37-41 and begins with the word Vayomer (And Said, Spoke).
In the ancient Temple, after the Shema' was read, all three paragraphs were then recited aloud by the Kohanim following the daily morning offerings. (Tamid 5:1). The people assembled in the Temple courtyard did not join in this reading, but on hearing the first sentence of the Shema', they responded with:
Baruch shem kevod malchuto l'olam va-ed!
Blessed is the Name of His Glorious Kingdom forever and ever!This response is not a quotation of any biblical verse though it bears some similarities to a verse in Tehillim 72:19. This became the response to all blessings recited by the Kohanim in the Temple, including the Priestly Blessing. It was used in lieu of "Amein." It was also the response to the declaration, "Hear O YIsarel, Hashem is our G-d, Hashem is One!" (Taanit 16b; Yoma 6:2, 3:8).
This response was later transferred to the Synagogue as a standard part of the Shema'. In order to indicate that this sentence is not part of the Biblical passage of the Shema', it is customary to say it in a more subdued voice than the rest of the Shema' (Pesachim 56a). The only exception to this is on Yom Kippur when it is deliberately said aloud.
Sources:
Artscroll Siddur
To Pray As A Jew - Donin