Avodah Zarah 5:12-Avos 1:1
Avodah Zara 5:12
If a Jew buys cooking utensils from a non-Jew, they must be kashered (kosherized) as follows: things that are typically immersed must be immersed; things that are used to boil must be boiled; things that are used in fire must be made white hot in fire. A spit and a grill must be made white hot in fire; a knife must be polished through abrasion and it becomes kosher.
Moshe received the Torah at Sinai. He transmitted it to Yehoshua, who transmitted it to the Elders. They transmitted it to the Prophets, who transmitted it to the Men of the Great Assembly. The latter said three things: Be deliberate in judgment, raise many disciples, and make a protective fence around the Torah.