Following this sublime path, we will now elaborate on the last part of the final essay of the Sefas Emes presented above. He connects the intent of Krias Shema with Yaakov Avinu, the epitome of “emet”: And Krias Shema emanates from the gathering of the community of Yisrael. For, the attestation regarding HKB”H is not made by a single person but only by the community of Yisrael. As it is written: “Shema Yisrael.” “Shema” is a gathering and assembly, and the name of Hashem, our G-d, rests on it; and it is destined to endure; as it is written: “Sefas Emes is established forever!”
With regards to the focus and intent of Krias Shema, the Avudraham writes: It is customary to say it aloud to enhance the focus of the first passuk, which is the essence of its intent. Also, it is the way testimony is given; as if every individual is saying to his fellow: “Listen, I believe that Hashem, our G-d, is the only One in His universe.” Hence, you find that the “ayin” of "שמע" is enlarged and the “dalet” of "אחד" is also enlarged, which spells "עד", alluding to testimony.
Furthermore, we know that the Shulchan Aruch rules (C.M. 34, 1): A rasha is not qualified to testify. That being the case, we can ask if any Jew is qualified to recite Krias Shema, attesting to the oneness of HKB”H. After all, the wisest of all men said (Koheles 7, 20): "כי אדם אין צדיק בארץ אשר יעשה טוב ולא יחטא"—for there is no man so wholly righteous on earth that he always does good and never sins. If this is true of a tzaddik, how much more so of someone who is not considered a tzaddik!
The answer is contained in the sacred, insightful words of the Sefas Emes just quoted: And Krias Shema emanates from the gathering of the community of Yisrael. For, the attestation regarding HKB”H is not made by a single person but only by the community of Yisrael. As it is written: “Shema Yisrael.” “Shema” is a gathering and assembly, and the name of Hashem, our G-d, rests on it. When we say “Shema Yisrael” out loud, we are gathering together and uniting. Thus, all Jewish neshamos ascend to the world of “Kol Yisrael,” where they are free of sin and wrongdoing. As such, each of us is qualified to give valid, truthful testimony regarding the oneness of HKB”H.
This explains beautifully the passage in the Zohar hakadosh (Terumah 135a): "רזא דשבת איהי שבת דאתאחדת ברזא דאחד, והא אוקימנא רזא דה' אחד ושמו אחד"—the mystery of Shabbas is that on Shabbas everything is united in the mystery of Oneness; as we have explained, this is the mystery (concealed meaning) of “Hashem is One and His name is One.” So, we see that Shabbas Kodesh and Krias Shema go hand in hand. On Shabbas, the universe of “Kol Yisrael” (the source of the neshamos of Yisrael) is revealed. We express this fact by reciting: "וינוחו בו כל ישראל"—and may “Kol Yisrael” rest on it. Similarly, by reciting Krias Shema, we gather together in unity to ascend to the universe of “Kol Yisrael.”