The deep night is named, in the Zoroastrian system, not for its darkness but for what ends it: Ushahin is the watch of Ushah, dawn, though it begins at midnight when dawn is furthest away. The naming is the theology. The hours when the powers of disorder press hardest are claimed in advance for the light that will defeat them, and the being who holds the line meanwhile is Sraosha, whose name means hearkening or obedience: the divine attentiveness itself, first of creation to worship Ahura Mazda, armed and vigilant, patrolling the world against the demons while humanity sleeps. Sraosha's vigil makes the watch the proper time for the religion's most strenuous liturgy, the Vendidad service, the six-hour recitation of the law against the demons performed within this gah precisely because the enemy it addresses is then strongest.
For the ordinary believer the watch asks less: those who wake in the night retie the kusti and say the Ushahin prayer, and the tradition, knowing the cost of leaving a warm bed, credits night prayer with special merit, a sentiment its neighbouring religions echo in the tahajjud of Islam and the vigils of Christian monasticism. The watch ends with the religion's most charming piece of sacred zoology: the rooster is Sraosha's creature, and his crowing before first light is understood as the yazata's summons, the whole animal creation joining the guardian of the night in waking the faithful to the day's first prayer.