Zoroastrian daily devotion is built on the gahs, the five watches that partition the twenty-four hours, and Havan opens the cycle with the day's working light. The name is liturgical to the letter: havana is the mortar and pestle of the haoma rite, and the morning watch is when the priesthood performs the Yasna, the central act of worship in which haoma is pressed, so the whole first quarter of the day carries the name of an implement of sacrifice. For the ordinary believer the watch's duty is the gah prayer.
Zoroastrian practice frames each watch with the kusti ritual, the untying and retying of the sacred cord over the sedreh, the white undershirt, with its accompanying prayers; to this the worshipper joins the Avestan prayer proper to the watch, and the Havan Gah text greets the ratu, the lord, of the morning. That lord is Mithra, the great yazata of covenant and of the sun's ordering light, invoked with his epithet of the wide pastures, and with him the watch honours Savanghi and Visya, spirits of profit and of the settlement, the humble genii of the productive morning. The theology is characteristic: the day's divisions are not neutral time but personified order, each watch a being to be greeted, so that simply living through a Zoroastrian day means saluting the structure of the good creation five times, beginning here, with the sun up and the mortar ringing in the fire temple.