Shab-e Chella(-e bozorg) (“night of (the great) forty”‎) or Shab-e Yalda (“Yalda night”‎) is an Iranian festival celebrated on the “longest and darkest night of the year,” that is, in the night of the Northern Hemisphere’s winter solstice. Calendarically, it is celebrated in the night between the last day of the ninth month (Azar) and the first day of the tenth month (Dae) of the Iranian civil calendar, which corresponds to the night of December 20 or 21 each year.

The longest and darkest night of the year is a time when friends and family gather together to eat, drink and read poetry (especially Hafez) until well after midnight. Fruits and nuts are eaten and pomegranates and watermelons are particularly significant. The red color in these fruits symbolizes the crimson hues of dawn and glow of life. The poems of Divan-e-Hafez, which can be found in the bookcases of most Iranians families, are intermingled with peoples’ life and are read or recited during various occasions like this festival and at Nowruz.

In the 1st-3rd centuries, significant numbers of Eastern Christians settled in Arsacid and Sassanid territories, where they had received protection from religious persecution. Through them, Western Iranians came in contact with Christian religious observances, including, it seems, Nestorian Christian Yalda, which in Syriac (a Middle Aramaic dialect) literally means “birth” but was also one of the Syriac words for Christmas, which — because it fell nine months after Annunciation — was celebrated on eve of the winter solstice. Although it is not clear when and where the Syriac word was adopted into Persian, gradually ‘Shab-e Yalda’ and ‘Shab-e Cheleh’ became synonymous and the two are used interchangeably.

An association with the 40-day “chella” period is preserved amongst Iranian Azerbaijanis, who call it Chilla Gejasi, which means the beginning of the first 40 days of winter. The Iranian concept also survives in Urdu-speaking Kashmir, India, where Chillai Kalan designates the 40-day harshest winter period.

In pre-Islamic Zoroastrian tradition the longest and darkest night of the year was a particularly inauspicious day, and the practices of what is now known as “Shab-e Chelleh/Yalda” were originally customs intended to protect people from evil (see dews) during that long night. People were advised to stay awake most of the night, lest misfortune should befall them, and people would then gather in the safety of groups of friends and relatives, share the last remaining fruits from the summer, and find ways to pass the long night together in good company. The next day (i.e. the first day of Dae month) was then a day of celebration. Although the religious significance of the long dark night have been lost, the old traditions of staying up late in the company of friends and family have been retained in Iranian culture to the present day.

Food plays a central role in the present-day form of the celebrations. In most parts of Iran the extended family comes together and enjoys a fine dinner. A wide variety of fruits and sweetmeats specifically prepared or kept for this night are served. Foods common to the celebration include watermelon, pomegranate, nuts, and dried fruit. These items and more are commonly placed on a korsi, which people sit around.

After dinner the older individuals entertain the others by telling them tales and anecdotes. Another favourite and prevalent pastime of the night of Chelleh is divination by the Divan of Hafez (fal-e Hafez). It is believed that one should not divine by the Divan of Hafez more than three times, however, or the poet may get angry.

Since the first night of winter ( 21th of December) is the longest night and from that night on the days get longer and the warmth and light of the sun increases, that night was supposed to be the time for the re-birth of sun. The Aryan tribes, in India, Iran and Europe celebrated sun’s birth at the beginning of winter. Yalda is a Syriani word meaning birth. The Roman used the word natalis for birth.

Sources
wikipedia
Tasnim News
ISNA
IRNA