Avoda Zara 72 - 76
Rav Nachman said in the name of Rabba bar Avuha, “Even new eating vessels purchased from gentiles require tevilah in a mikveh according to Torah law.”
Although the gemara explains the source of “tevilat keilim” (ritual immersion) as referring to vessels already used by gentiles with non-kosher food, we can apply this source to new vessels as well: Once the used vessels have been kashered in the appropriate way, they are considered as new and nevertheless need tevilah, as taught in a bereita in our sugya. It follows that vessels that are new to begin with should also require tevilah in a mikveh.
- Avoda Zara 75b