A boil or a burn may become unclean in a week and by two signs: by white hair or by a spreading. What is a "boil"? An injury received from wood, stone, peat, or the waters of Tiberias, of from any other object whose heat is not due to fire is a boil. What exactly is a "burn"? A burn caused by a live coal, hot embers, or any object whose heat is due to fire is a burning.

A boil and a burn do not combine, nor do they spread from one to the other, nor do they spread from there to the skin of the flesh, nor does [a nega] on the skin of the flesh spread to them. If they were festering they are clean. If they formed a scale as thick as garlic peel, such is the scar of the boil that is spoken of in the Torah. If they were subsequently healed, even though there was a mark in their place, they are regarded as the skin of the flesh.

They asked R. Eliezer: "[What is the ruling concerning] one who had a bright spot the size of a sela form on the inside of his hand and it covered up the scar of a boil?" He replied: "He should be isolated." They said to him: "Why? Since it is neither capable of growing white hair nor can it effectively spread nor does quick flesh cause it to be unclean?" He replied, "It is possible that it will contract and then spread again." They said to him, "But what about when its only the size of a split bean?' He said to them: I have not heard anything. Rabbi Judah ben Batera said to him, "Can I teach something about this?" He replied, "If you would thereby confirm the ruling of the sages, go ahead." He said, "Lest another boil would arise outside it and spread into it. He replied: "You are a great scholar for you have confirmed the words of the sages."