http://en.wikipedia.org/wiki/Chaharshanbe_Suri

Chahārshanbe-Sūri (Persian: چهارشنبه ‌سوری‎, pronounced Chārshambe-Sūri) meaning Wednesday Feast, from the word sour which means feast in Persian,^[1] or more plausibly, consider sūr to be a variant of sorkh (red) and take it to refer either to the fire itself or to the ruddiness (sorkhī), meaning good health or ripeness, supposedly obtained by jumping over it,^[1] is an ancient Iranian festival dating back to at least 1700 BCE of the early Zoroastrian era.^[2] Also called the Festival of Fire, it is a prelude to Nowruz, which marks the arrival of spring. The words Chahar Shanbeh mean Wednesday and Suri means red. Bonfires are lit to "keep the sun alive" until early morning.^[3] The celebration usually starts in the evening, with people making bonfires in the streets and jumping over them singing zardi-ye man az to, sorkhi-ye to az man. The literal translation is, my sickly yellow paleness is yours, your fiery red color is mine. This is a purification rite.^[4] Loosely translated, this means you want the fire to take your paleness, sickness, and problems and in turn give you redness, warmth, and energy. There are Zoroastrian religious significance attached to Chaharshanbeh Soori and it serves as a cultural festival for Iranian people: Persian Jews, Persian Muslims, Persian Armenians, Kurds, and Zoroastrians.

Another tradition of this day is to make special ajeel, or mixed nuts and berries. People wear disguises and go door to door knocking on doors as similar to Trick-or-treating. Receiving of the Ajeel is customary, as is receiving of a bucket of water.

Ancient Iranians celebrated the last 5 days of the year in their annual obligation feast of all souls, Hamaspathmaedaya (Farvardigan or popularly Forodigan). They believed Faravahar, the guardian angels for humans and also the spirits of dead would come back for reunion. There are the seven Amesha Spenta, that are represented as Haftseen or literally the seven S. These spirits were entertained as honored guests in their old homes, and were bidden a formal ritual farewell at the dawn of the New Year. The festival also coincided with festivals celebrating the creation of fire and humans. In Sassanid period the festival was divided into two distinct pentads, known as the lesser and the greater Pentad, or Panji as it is called today. Gradually the belief developed that the 'Lesser Panji' belonged to the souls of children and those who died without sin, whereas 'Greater Panji' was truly for all souls.