Elbogen's standard history of the Jewish prayer service traces how these two verses, with the paragraphs that follow them in Deuteronomy and Numbers, became a fixed twice daily recitation rather than an occasional reading. The Mishnah already assumes the practice is old: it debates from what hour in the evening and what hour in the morning a worshipper may recite the Shema, arguing about the boundary rather than about whether the obligation exists at all, which suggests the twice daily rhythm predates the debate itself. The three paragraphs sit inside their own frame of blessings, said before and after, so that what began as scripture became liturgy, structured recitation rather than reading.
Tradition holds that the Shema is also said at the deathbed, and that Rabbi Akiva recited it while being executed by the Romans, prolonging the word ehad, one, until his breath gave out, a story that made this line the one Jewish martyrdom is remembered as ending on. Whatever the historical event behind the story, its endurance shows how completely the Shema became identified with the whole of Jewish devotion rather than with one command among many.
Elbogen's history also traces how the liturgy grew its own frame around these verses over the centuries, blessings recited before and after that differ between the morning and the evening service, so that a worshipper reciting the Shema today says words that accreted onto this text long after Deuteronomy itself was written, an ordinary case of a scripture becoming a rite through repeated use rather than through any single act of composition.