Mishnah Hagigah 2.1 (trans. A.Y. Reed)

It is not permitted to expound the laws of prohibited sexual relationships [Lev 18:6-23] among three, nor Ma‘aseh Bereshit (lit. "Work of Creation" = Gen 1) among two, nor the Merkavah (lit. "Chariot" = Ezek 1; 10) among one, unless he is wise [ofj] and understands on his own.

Anyone who speculates aboutfour things, it would be merciful for him if he had not come into the world: what is above , what is below, what is before, what is after. Anyone who has no concern for the honor of his Creator, it would be merciful for him if he had not come into the world.

Mishnah Sanhedrin 10 (trans. from Soncino edition)

All Israel28 have a portion in the World to Come,29 for it is written, Thy people are all righteous; they shall inherit the land for ever, the branch of my planting, the work of my hands, that I may be glorified.’30 But the following have no portion therein: he who maintains that resurrection is not a biblical doctrine,31 the Torah was not divinely revealed, and an epikoros.32 R. Akiba added: one who reads uncanonical books.33 Also one who whispers [a charm] over a wound and says, I will bring none of these diseases upon thee which I brought upon the Egyptians: for I am the Lord that healeth thee.’34 Abba Saul says: also one who pronounces the divine name as it is spelt.35

Three kings and four commoners have no portion in the World to Come: the three kings are Jeroboam, Ahab, and Manasseh.36 R. Judah said: Manasseh hath a portion therein, for it is written, ‘and he prayed unto him, and was entreated of him, and he hearkened to his supplication and they restored him to Jerusalem, to his kingdom.37 They [the Sages] answered him: they restored him to his kingdom, but not to [his portion in] the World to Come. Four commoners, viz., Balaam, Doeg, Ahitophel, and Gehazi.38

The Generation of the Flood has no portion in the future world, nor will they stand at the [last] judgment, as it is written, [and the Lord said,] my spirit will not always enter into judgment with man:27 there will be neither judgment nor [my] spirit for them.28 The Generation of the Dispersion have no portion in the future world, as it is written, so the Lord scattered them abroad from thence upon the face of all the earth:29 ‘so the Lord scattered them abroad’, refers to this world, ‘and from thence did the Lord scatter them abroad’,30 to the World to Come. The men of Sodom have no portion in the future world, as it is written, but the men of Sodom were wicked and sinners before the Lord exceedingly:31 ‘wicked in this world, and ‘sinners’ in the World to Come;32 yet will they stand at judgment.

R. Nehemiah said: neither [the Generation of the Flood nor the men of Sodom] will stand at judgment, as it is written, therefore the unGodly shall not stand in the judgment, nor sinners in the congregation of the righteous:1 therefore ‘the unGodly shall not stand in the judgment’, refers to the Generation of the Flood; nor sinners in the congregation of the righteous’, to the men of Sodom. They [the Sages] answered him: they will not stand in the congregation of the righteous, but they will stand in the congregation of the wicked.2 The Spies have no portion in the World to Come, as it is written, even those men that did bring up the evil report upon the land, died by the plague before the Lord.3 ‘[they] died’ — in this world, ‘by the plague’ — in the World to Come.4 The Generation of the Wilderness have no share in the future world and will not stand at the [last] judgment, as it is written, in this wilderness they shall be consumed, and there they shall die:5 this is R. Akiba's view. R. Eliezer said: concerning them it is said, gather my saints together unto me; those that have made a covenant with me by sacrifice.6 The congregation of Korah is not destined to ascend [from the earth], as it is written, and the earth closed upon them’ — in this world, ‘and they perished from among the congregation’ — in the next:7 This is R. Akiba's opinion. R. Eliezer said: of them it is written, the Lord killeth, and maketh alive: he bringeth down to the grave, and bringeth up.8

The Spies have no portion in the World to Come, as it is said, even those men that did bring up the evil report upon the land, died by the plague before the Lord:4 died [implies] in this world; by the plague — in the next.5 The assembly of Korah have no portion in the World to Come, as it is written, and the earth closed upon them, [implying] in this world, and they perished from among the congregation — in the next — this is R. Akiba's view. R. Eliezer said: of them the writ saith, the Lord killeth and maketh alive: he bringeth down to the grave, and bringeth up.6

The ten tribes will not return [to Israel], for it is said, and cast them into another land, as is this day:10 just as the day goes and does not return, so they too went and will not return: this is R. Akiba's view. R. Eliezer said: as this day — just as the day darkens and then becomes light again,11 so the ten tribes — even as it went dark for them, so will it become light for them.

The inhabitants of a seduced city have no portion in the World to Come, as it is written, certain men, the children of Belial, are gone out from among you, and have withdrawn the inhabitants of their city.18 they are not executed unless the seducers are of that city and that tribe, and the majority thereof are seduced, and the seducers are men. if women or minors seduced it, if a minority were seduced, or if the seducers were from without the city, they19 are treated as individuals, and two witnesses and a formal warning are necessary for each [offender]. in this [the penalty of] individuals is severer than [that of] a multitude, for individuals are stoned, therefore their property is saved; but multitudes are decapitated; hence their possessions are destroyed.

Thou shalt surely smite the inhabitants of that city with the edge of the sword.20 A company of ass-drivers or camel-drivers passing from place to place saves it.21 Destroying it utterly, and all that is therein, and the cattle thereof: from this it was deduced that the property of the righteous, which is within [the city] is destroyed, but that which is without is saved, whilst that of the wicked, whether within or without, is destroyed.22 And thou shalt gather all the spoil thereof in to the midst of the public square thereof etc.23 If it had no public square, one is made for it; if it was [situated] without [the town], it is brought within it,24 as it is said, and thou shalt burn with fire the city, and all the spoil thereof every whit, for the Lord thy God.25

‘The spoil thereof’ implies, but not the spoil of heaven. Hence it was ruled, the holy objects therein26 must be redeemed; the terumoth27 allowed to rot; and the second tithe28 and the sacred writings hidden.29 A whole-offering for the Lord thy God:30 R. Simeon said: the Holy One, blessed be He, declared, if ye execute judgment upon the seduced city, I will ascribe merit to you as though ye had sacrificed to me a whole offering. and it shall be a heap for ever:,31 [hence] it may not be converted into gardens and orchards: this is the view of R. Jose the Galilean. R. Akiba maintained: it shall not be built again [implies] that it may not be rebuilt as it was, but may be converted into gardens and orchards. And there shall cleave nought of the cursed thing to thine hand: [that the Lord may turn from the fierceness of his wrath, and shew thee mercy]:32 as long as the wicked exist in the world, there is fierce anger in the world; when the wicked perish from the world, fierce anger disappears from the world.