Dear Rabbi,

I am sleeping over at the home of someone who does not keep the kosher dietary laws. May I use their cups to do the ritual hand washing and to drink from? Or do the cups have to be kosher?

Answer:

There's no problem with using any cup for washing your hands.

When it comes to drinking, it is best to use a disposable cup. However, should you need to, you may drink cold drinks from a clean cup. In the home of a Jew, one should use a plastic or wooden cup. The reason is because a glass, metal or ceramic cup needs to be immersed in a mikvah, a ritual bath or a large natural body of water, before drinking from it. See Immersing Utensils.

This does not apply during Passover, when one should be more careful not to use any cups, besides disposable ones, that are not kosher for Passover.

Please see How do I keep a kosher kitchen when my husband still wants to cook shrimp? from our site dedicated to the kosher dietary laws.

All the best.

Rabbi Zalman Nelson
Ask the Rabbi @ The Judaism Website – Chabad.org