Seventy Two Threads, Woven So the Wearer Counts Them by Feel

The kusti is a sacred cord, woven flat and hollow from seventy two strands of lambswool, a number read as corresponding to the seventy two chapters of the Yasna, the central liturgical collection of the Avesta. It is wrapped three times around the waist over the sudreh and fastened with a sequence of ritual knots at the front and back rather than tied off casually. Lambswool is specified rather than any other fiber, and traditional practice ties this to the animal's standing in Zoroastrian ethics as a creature of Ahura Mazda under the wearer's care.

The cord is woven by hand, historically by women of priestly families, on a small fixed loom, and the physical count of the threads is meant to be perceptible to the fingers so that the retying can be performed correctly without needing to see it, which matters because the kusti is retied as part of prayers said before dawn and in low light. Boyce's survey of Zoroastrian textual and devotional sources situates the seventy two thread count among a wider set of numerically encoded garments in the tradition, where the object itself is built to carry a piece of doctrine in its construction rather than only in what is said about it. The finished cord is checked by the wearer before use, since a flaw in the weave is considered to compromise its function.