The Red String

No classical Kabbalistic source actually prescribes this practice. An early rabbinic text lists a red thread specifically as an example of a superstition to be avoided — the tradition's own earliest recorded verdict on the practice is a prohibition, not an endorsement, and the mass-market bracelet itself only dates from one organisation's 1990s marketing.

Tosefta Shabbat 7:1, listing the red thread as a forbidden Amorite custom