it is yom kippur, a holiday of which i have little knowledge.

yom kippur is a complete sabbath; no work can be performed on that day. it is well-known that you are supposed to refrain from eating and drinking (even water) on yom kippur. It is a complete, 25-hour fast beginning before sunset on the evening before yom kippur and ending after nightfall on the day of yom kippur. the talmud also specifies additional restrictions that are less well-known: washing and bathing, anointing one's body (with cosmetics, deodorants, etc.), wearing leather shoes (orthodox jews routinely wear canvas sneakers under their dress clothes on yom kippur), and engaging in sexual relations are all prohibited on yom kippur. - from jewfaq.org