KITEL (Yid. "gown"), white garment worn in some Ashkenazi rites by worshipers during the prayer service on the High Holidays (*Rosh Ha-Shanah and the *Day of Atonement), and by the ḥazzan at the Musaf service on Shemini Aẓeret, the eighth day of *Sukkot (when the prayer for rain is recited) and the first day of *Passover (when the prayer for dew is recited). It is also worn, in some rites, by the person conducting the *seder on Passover eve and by the groom during the *marriage ceremony. Formerly a white garment was worn every Sabbath and on all solemn occasions (tj, rh 1:3). The association of the color white with the notion of purity (and hence also forgiveness of sins) and solemn joy contributed to the special use of the kitel on all these occasions. The day of marriage is considered a day of atonement for the groom and the bride, and the idea of atonement and penitence is also associated with that of death. The white kitel is therefore also part of the raiment in which the dead are clothed for burial. In some communities, the kitel is also called sargenes, either because it was made of a material called serge or sericum (see: Rashi to Shab. 77b), or because its origin from the German word Sarg (coffin) denotes a garment of death.
Eisenstein, Dinim, 364.