The Zoroastrian / Mazdayasnian sacred bath of is called the nahn. Before it is performed, the Padyab-kusti (tying of the kusti) is performed by both the bather and the priest. This ritual involves untying and re-tying the Mazdayasnian sacred thread, the kusti, which is worn about the waist at all times except when bathing. The priest must possess a special liturgical qualification, the Khub, and he must have performed the extremely elaborate Barashnom ceremony in the past without having thereafter done any actions which would invalidate it.
The bath usually takes place at the house of the bather or in a Fire Temple. After doing the Padyab-kusti, the bather sits on a stool which is usually made of stone. The bather recites the Baj, which is the grace said before meals. Then they are given a pomegranate leaf to chew or eat. It is given to them on a handkerchief or the lower part of shirt so that the priest does not have to touch them. This leaf symbolizes plant kind and the Ameshaçpenta Ameretat. Once they are done with the leaf, the Mazdayasnian is given Nirangdin, which is consecrated bull urine. This might seem unsanitary, but according to Mazdayasnian doctrine it is made entirely sanitary and even holy if the consecration is done properly. Before drinking, the Mazdayasnian says in Avestan, “I drink this for the purification of my body, for the purification of my soul.” This is said three times, and between each saying the bather drinks a very small quantity of the Nirangdin. Then they say the post-meal grace, and perform the Padyab-kusti again.
The bather now says the Patet, the prayer of repentance. Then they go to the bathroom and undress after saying Khnaothra Ahurahe Mazdao (I do this for the pleasure of Ahura Mazda) and the Ashem Vohu. They recite the Sraosha Baj while holding their right hand over their head, because Mazdayasnians are not supposed to speak with their head uncovered. This prayer begins with a request for Sraosha to hear the prayer, followed by a repentance. The prayer is interspersed with many Ahuna Vairyas and Ashem Vohus. Various Yazatas are praised, and Ahura Mazda is asked for help and blessings. After this prayer is completed, the bather is handed several items on a long stick called a naogar, so that the priest does not have to see their nakedness. The naogar has nine knots, the symbolism of which is unknown to me, and a spoon at the end. Sometimes the items are left in the bathroom in advance, especially when the bather is female. The first item given is Nirangdin, which is given three times and rubbed on the body. Then the bather is given sand thrice, to rub on their body. Lastly, they are given consecrated water thrice, which they rub on their body. The consecrated water may also be sprinkled on the new clothes which the bather is to put on after the bath. Lastly, the bath itself is taken in consecrated water. The whole bath is consecrated by the introduction of a small number of consecrated water drops. After the bath, the bather puts on their clothes, recites some prayers of gratitude, and does the Padyab-kusti.
 J.J. Modi and others have suggested that sand was originally used only as a substitute for water.