English Explanation of Mishnah Sanhedrin 7:2

The manner in which burning is executed is as follows: They would lower him into dung up to his armpits, then a hard cloth was placed within a soft one, wound round his neck, and the two loose ends pulled in opposite directions, forcing him to open his mouth. A wick was then lit, and thrown into his mouth, so that it descended into his body and burned his bowels.
R. Judah says: “Should he have died at their hands [being strangled by the bandage before the wick was thrown into his mouth], they would not have fulfilled the requirements of execution by fire. Rather his mouth was forced open with pincers against his wish, the wick lit and thrown into his mouth, so that it descended into his body and burned his bowels.
Rabbi Eleazar ben Zadok said: “It once happened that a priest's daughter committed adultery, whereupon bundles of sticks were placed around her and she was burnt. The Sages said to him: “That was because the court at that time was not well learned in law.
Our mishnah describes how execution by burning was to be carried out. It might be helpful to begin with Rabbi Eleazar ben Zadok (section three), who testifies to having seen a priest’s daughter executed by being totally burnt (evidently alive). This follows the seemingly simple requirement mentioned in Lev. 21:9, that a priest’s daughter who committed adultery should be burned. However, the Sages who disagree with him, and those who state their opinion in section one, believed that execution by burning was to be done by burning up the insides of the person. They would open up his mouth and throw burning material inside and it would descend and burn him from the inside. Rabbi Judah’s dispute with the Sages is with regards to the manner in which they would force open his mouth; he does not disagree with the Sages general understanding of how execution by burning was carried out. Rabbi Judah is concerned lest in the process of opening his mouth they strangle him which is a different form of execution.
It is worth discussing briefly the nature of the two different understandings of death by burning. The Rabbis prescribe a form of burning that doesn’t seem to be the simple understanding of the Torah. When the Torah states that someone is to be burned, it probably means an execution similar to that referred to by Rabbi Eleazar ben Zadok in section three. Therefore the question needs to be asked: why did the Rabbis insist that burning would take place by burning the inside and not the outside? The answer is probably not that one form of death was more or less painful than the other. They both sound quite painful. The best answer that is borne out by many other sources, is that the Rabbis did not want to sanction an execution in which the outer body was disfigured. While they believed in the death penalty (again, at least theoretically) they wanted to execute the criminal while doing as little physical, external damage to the body as possible. The body, after all, is a gift from God, and while the person may deserve death according to the law, damaging the body serves no purpose. This is to be contrasted to other cultures that have existed until this very day, who considered the public disfiguring of the body of the criminal to be desirable, either as an example to the rest of society, or as a means to take vengeance even on the corpse. The Rabbis took a strong stand against such practices, one that we will see in several places. Indeed we have already seen this attitude in the previous chapter, when it stated that the hanged body was to be taken down immediately. Although the criminal deserved to die, mutilating his body was indeed, according to Jewish law, an affront to God.