Jesus spoke about Gehenna. In the book of Jeremiah, Gehenna(valley of the sons of Hinnom) was a place where Judah broke the law by sacrificing children to the god Molech. This was an abomination and the very worst example of violating the law. Therefore, it also became the very worst example of the curses of the law for Jeremiah said the same valley would be filled with the corpses of the inhabitants of Judah when the Babylonians would invade.
Jesus said that those in Israel such as the Pharisees and scribes who snared little ones from believing in Him, that it would be better for all concerned if these snares(Pharisees, scribes, etc) were cut off from Israel, had a mill stone hanged about their necks and cast into the sea. He then goes on the illustrate this by saying, if your eye snares you, or your hand snares you, etc., it’s better to cut off the offending part of the body than for your whole body to go through the fires of Gehenna. He wasn’t saying that an individual should pluck out their eye, or cut off their hand, rather, He was saying that it would be better for the whole body of Israel to cut off the snares and offenders than for the whole body of Israel to suffer the curses of the law. Those curses where things like destruction at the hands of their enemies, loss of the promised land, and exile among the nations. This is what the whole body of Israel experienced in 70Ad when the Romans destroyed their nation.
Moses told Israel that any Israelite who tried to entice(snare) his brethren into idolatry should be cut off from among the people so that the entire nation should not suffer the curses of the law. Jesus is saying the exact same thing with respect to how the Pharisees and scribes were trying to keep Israel from believing in Him. Read Matthew 23 in this light. “And you! Fill full the measure of your fathers! Serpents! Progeny of vipers! How may you be fleeing from the judging of Gehenna?….All these things will be arriving on this generation…Lo! left is your house desolate…”(Matt 23:32-24:2)