In Judaism, washing the hands (Netilat Yadayim) and the use of wash cups is part of the religious rituals of believers. The general basis for washing of the hands in Jewish law is derived from Leviticus 15:11, which is an admonishment for washing of hands to become clean following impure activities.
The modern practice of using a wash cup is to pour water on the hand three times. The wash cup is used and the water is poured between alternate hands. This practice is known by the Yiddish phrase negel vasser, which translates to "nail water." The use of a special wash cup is called for during the practice.
Blessing and Wash Cups
When using a wash cup, practicing Jews say a blessing in Hebrew that translates to "Blessed are you, Hashem our God King of the universe who has sanctified us with his commandments and has commanded us concerning the elevation of hands."
Wash Cups and Meals
Two types of washing of the hands can be practiced, depending on which community the practicing person is from, and most practicing Jews wash both before and after a meal. In some circles, not washing before meals is equivalent to being unchaste and can incur a divine penalty in the form of poverty or destruction. Washing after meals is seen as a health need, since it is believed that not to do so can cause blindness.
Notably, washing after meals is more of a contemporary addition to the ritual than a historical one, since it had fell out of practice but has seen resurgence in observance in recent times. This is especially true during Jewish holidays and the Shabbat, when greater numbers of followers eating special meals tend to follow these rituals.
A third ritual hand washing using a wash cup is added to the Passover Seder. It is required to wash before eating the green vegetable, since it is considered to be separate from the meal itself.
Hand Washing Before Worship
Based on the ritual purification ritual of traditional Judaism, a person should wash both of his/her hands before praying upon entering the temple. In Orthodox Judaism, prayer serves instead of hand washing. It is worth noting before performing the duties of their offices, member of the synagogue are required to wash their hands—a ritual that draws its requirement straight from the Torah.
Other Occasions for Washing Hands
Upon rising, it is customary for Jews to wash their hands. It is also important in Judaism for the washing of hands after visiting the bathroom (of course) for removing impurities and keeping the body clean. After cutting the nails or hair, hand washing is required, or after touching a part of the body that is normally covered. Touching the inside of the ear, nose, or touching the scalp is call for washing the hands. Jews are also expected to wash their hands after participating in a funeral procession, including when leaving the cemetery, and after coming within close proximity of the dead person.
Two-Handled Wash Cups
Some Jewish communities practice the use of two-handled wash cups. This is due to the belief that the first hand is washed, making it pure and clean, but the unwashed hand is not pure and clean—so neither should touch. However, when using a cup with one handle, the clean hand becomes dirty again once the dirty hand touches the handle. The two-handled wash cup remedies this by making it simple for the two hands to avoid touching one another.