Q1: I was making tea (pareve), and poured boiling water into a dairy mug (there was no milk in the mug). I then remembered that the water for the tea was boiled in a clean meat pot. What do I do?

A1: There is no problem with the pot. The question is on the mug. Perhaps the water absorbed meat taam (taste) and transferred that meat taam into the dairy mug rendering it unkosher. Although the Rama (Y.D. 95:3) states that the mug needs to be kashered, many poskim disagree (e.g. Shach, Pri Chadash). We generally follow the Aruch HaShulchan who concludes that the mug should be kashered if possible. If the mug is made of a material that cannot be kashered, you may clean it out then set is aside for 24 hours. After that time you may use it without kashering it. 

Q2: Does the concept of ben yomo (see Practical Halacha OF THE MONTH - AV) make a difference here?

A2: Yes. The above discussion assumes that both the pot and the mug are ben yomo. If either one is not ben yomo then the mug need not be kashered and there is no need to wait 24 hours.

A3: If there was actual meat in the pot (albeit small remnants) then the absorbed meat taam of the water is much more intense and the mug MUST be kashered. If there was dairy in the mug then the mug SHOULD be kashered. 

Questions? You can contact Rabbi Lederman at (858) 613-0222 or RBL613@Juno.com