The custom of wearing a kittel—a snow-white robe—at a wedding belongs to the Ashkenazi tradition (that of Jews of Central and Eastern Europe). It is also widespread among Hasidim of various groups.
Among Sephardim (Jews of the Iberian Peninsula and the Middle East), as well as other Eastern Jewish communities (such as Yemenite or Bukharan Jews), this custom is not practiced. A Sephardic groom does not wear a kittel under the chuppah and, as a rule, does not fast on his wedding day.
Within the Ashkenazi community itself, the rules may vary slightly depending on the particular religious tradition.
Putting On the Kittel Before the Chuppah
This ritual takes place at the very beginning of the wedding, during Kabbalat Panim, before the badeken ceremony. The groom is in the men's section of the hall, where the marriage contract (ketubah) is signed. Before he goes to the bride, the fathers or close friends help the groom put on the kittel—a long white ceremonial robe made of cotton or linen.There are several explanations of the meaning of this custom:
The Day of Atonement (Yom Kippur): For the bride and groom, their wedding day is their personal Day of Judgment. All their past transgressions are forgiven, and they begin life with a clean slate. The white kittel symbolizes this absolute spiritual purity. Men wear the very same kind of kittel during prayer on Yom Kippur.
A Change of Status: The kittel sets the groom apart from the guests. White is the color worn by the High Priest when entering the Holy of Holies. Thus, the kittel emphasizes the groom's holiness at the most important moment of his life—when he is preparing to fulfill the Creator's commandment and establish a new family.
Humility and Remembrance of Eternity: The white shroud in which people are buried in Jewish tradition looks almost the same as a kittel. By wearing it on the day of his greatest joy, the groom reminds himself of life's transience and that spiritual values, rather than a materialistic ego, should be the main priority in marriage.