Judaism has no creed in the Christian sense, no text drawn up by an assembly to settle a dispute and imposed as a test. What it has instead is a verse of Torah that liturgy raised into that role. Hear, O Israel, the Lord is our God, the Lord is one, from the sixth chapter of Deuteronomy, is what a Jew says twice a day, teaches to a child first, and says last.
The liturgical Shema is longer than the one famous line. It joins three passages: Deuteronomy 6:4 to 9, which commands that these words be taught, bound and written; Deuteronomy 11:13 to 21, on the consequences of keeping or abandoning the commandments; and Numbers 15:37 to 41, on the fringes worn as a reminder. Read together they are not a statement of belief but an acceptance of obligation, which the rabbis call taking on the yoke of the kingdom of heaven.
Its antiquity in this role is well evidenced. The Mishnah opens its very first tractate not by asking whether the Shema should be recited but from what hour in the evening it may be, which is the grammar of a practice already old. The Nash Papyrus, an Egyptian fragment from the Second Temple period, carries the Ten Commandments and the opening of the Shema together, which suggests a devotional use of the text well before the rabbinic prayer book existed.