There is a sentence a devout Jew in the first century said upon waking and said again upon lying down, the closest thing the faith had to a creed. It comes from Deuteronomy, and it begins with the command Shema — “hear” — the way a parent says listen. In Hebrew: שְׁמַע יִשְׂרָאֵל יְהוָה אֱלֹהֵינוּ יְהוָה אֶחָד — shema yisrael, YHWH eloheinu, YHWH echad. “Hear, O Israel: the LORD our God, the LORD is one.” And the last word, the one the whole confession lands on, is אֶחָד (echad) — one.

This wasn’t a line of poetry tucked into a long book. It was the center of gravity of an entire people’s faith. Bound to the forehead and the arm, fixed to the doorpost, taught to children before they could read, recited morning and evening. To be a Jew in that world was, more than anything, to be a person who said the LORD our God, the LORD is one — and to say it in a world crawling with rival gods. Step into any city of the empire and you’d pass temples to Zeus, to Artemis, to Caesar; you’d smell the sacrifices and watch the processions. Through all of it the Jew walked saying: one. Our God is one. The rest are not gods at all.

Scholars call this strict monotheism, and one careful student of it draws a distinction worth keeping: the Jewish concern was less about what God is — what abstract stuff he’s made of — than about who God is. Israel’s God held a unique identity. He alone made all things, ruled all things, was to be worshiped. To say “the LORD is one” was to say there is exactly one being who holds that identity, and everything else in heaven and earth stands on the creature side of the line.

When the confession passed into Greek for the Greek-speaking Jews who made up much of the early Christian audience, אֶחָד became εἷς (heis) — “the Lord our God, the Lord is one,” heis. That’s the bridge: the Hebrew echad of the Shema becomes the Greek heis, and the monotheism of Deuteronomy travels intact into the language of the New Testament. So when Jesus prays that eternal life is to know “the only true God” (John 17:3), a Jewish ear hears no novelty. It hears the Shema in fresh words — the genuine God against the counterfeit gods of every city. Echad is the bedrock the whole confession rests on: not three gods, not many, but the LORD, and the LORD is one.