The Ben Ish Chai (Rabbi Yosef Chayim of Baghdad, 1833-1909), in his work Od Yosef Chai (Parashat Vaera, Halacha 3), discusses the precise intention one must have as he recites the first verse of Shema ("Shema Yisrael, Hashem Elokeinu Hashem Echad"). He writes (listen to audio for precise citation) that the recitation of this verse includes two declarations. First, we express "Kabbalat Ol Malchut Shamayim" – our acceptance of the yoke of Divine Kingship. This acceptance is expressed in the words "Hashem Elokeinu" – "Hashem our God" – whereby we proclaim our subjugation to God's authority. The second declaration we make when reciting this verse – "Hashem Echad" ("Hashem is one") – avows our belief in the oneness of God, the fact that there is no other power or creator.
Thus, the verse of "Shema Yisrael" should be understood to mean: "Understand, Israel: we accept God as our King, and there is none other like God."
The Ben Ish Chai adds that this understanding of the verse helps explain why the letter "Ayin" in the word "Shema" and the letter "Dalet" in the word "Echad" are enlarged in the Siddur. These two letters spell the word "Eid," or "witness." Through the recitation of this verse, we testify to these fundamental tenets of Jewish faith: our subjugation to divine rule, and the oneness of God.
If one did not concentrate when he recited the first verse of Shema, must he recite it again with concentration?
The Sefer Chasidim (by Rabbi Yehuda Ha'chasid, Germany, 1150-1217), in Siman 18, rules that in such a case one must, in fact, repeat the first verse of Shema. He adds that this should be done in a low, inaudible voice, so that the people sitting nearby will not hear the repetition and mistakenly conclude that the person refers to two deities, Heaven forbid. This is the ruling as well of the Bayit Chadash (commentary to the Tur by Rabbi Yoel Sirkes, Poland, 1561-1640). The Taz (commentary to the Shulchan Aruch by Rabbi David Halevi, Poland, 1586-1667), however, ruled that one should instead pause for a brief period and then repeat the verse aloud. Since he makes an interruption in between the two recitations, it is clear that he intends merely to repeat the verse, and does not refer to two deities. One should pause in such a case for the amount of time required to walk 22 cubits (approx. 40 feet), or roughly a half-minute.
When reciting the first verse of Shema, one should cover his eyes with his right hand. The Ben Ish Chai emphasizes that even those who are left-handed should cover their eyes with their right hand, rather than their left.
Later (Halacha 5), the Ben Ish Chai rules that although women are exempt from the obligation of Shema, as it falls under the category of "time-bound" Mitzvot, they are nevertheless included in the obligation of "Kabbalat Ol Malchut Shamayim" – to declare their acceptance of Divine Kingship. Therefore, women must recite the first verse of Shema each day. Preferably, the Ben Ish Chai adds, they should recite as well the verse of "Baruch Shem Kevod" which we recite after the verse of "Shema Yisrael."
Summary: When reciting the first verse of Shema, one should cover his eyes with his right hand even if he is a lefty, and concentrate on the meaning of the verse, namely, that he accepts the yoke of Divine Kingship and affirms his belief in the oneness of God. If one did not concentrate on the meaning of the verse, he must repeat it, either in a low voice or after a brief pause. Women are required to recite the first verse of Shema each day, and should preferably recite as well the verse of "Baruch Shem Kevod…"
