The Sh'ma contains the one verse of Scripture that probably every Jew in the world knows by heart, or has at least heard often, Deuteronomy 6:4:
Hear, O Israel, the Lord our God, the Lord is One.
The observant Jew says it in the morning and at nightfall every day of his life, with three related passages from the Torah. It is the first Hebrew sentence a child learns, and it is the utterance with which every Jew is supposed to breathe his last.
On this point I will obtrude a short personal anecdote. I used to wonder whether, in the last extremity, a man could really call to mind and recite the Creed. Then once during a typhoon in the Pacific I was almost blown off the deck of a ship, and I remember quite clearly thinking, as I went sliding toward my fate, "Well, if I drown, let me say the Sh'ma as I go." Luckily for me the lifeline I grabbed happened to hold; and so I postponed the utterance, and the world has a few plays and novels it could well have wagged along without, and the patient reader is enduring the present harangue. I believe there are one or two literary critics who may wish I had gotten to say that watery Sh'ma, but I cannot help that, a man hangs on if he can.