Jewish Encyclopedia, Gehenna
The place where children were sacrificed to the god Moloch … in the "valley of the son of Hinnom," to the south of Jerusalem (Josh. xv. 8, passim; II Kings xxiii. 10; Jer. ii. 23; vii. 31-32; xix. 6, 13-14). … the valley was deemed to be accursed, and "Gehenna" therefore soon became a figurative equivalent for "hell." Hell, like paradise, was created by God (Sotah 22a);[“Soon” in this verse would be about 700 BC +/-]
[Note, this is according to the ancient Jews, long before the Christian era, NOT supposed bias of Christian translators. DA]
(I)n general …sinners go to hell immediately after their death. The famous teacher Johanan b. Zakkai wept before his death because he did not know whether he would go to paradise or to hell (Ber. 28b). The pious go to paradise, and sinners to hell(B.M. 83b).
But as regards the heretics, etc., and Jeroboam, Nebat's son, hell shall pass away, but they shall not pass away" (R. H. 17a; comp. Shab. 33b). All that descend into Gehenna shall come up again, with the exception of three classes of men: those who have committed adultery, or shamed their neighbors, or vilified them (B. M. 58b).[/i]
… heretics and the Roman oppressors go to Gehenna, and the same fate awaits the Persians, the oppressors of the Babylonian Jews (Ber. 8b). When Nebuchadnezzar descended into hell, [שאול/Sheol] all its inhabitants were afraid that he was coming to rule over them (Shab. 149a; comp. Isa. xiv. 9-10). The Book of Enoch [x. 6, xci. 9, etal] also says that it is chiefly the heathen who are to be cast into the fiery pool on the Day of Judgment (x. 6, xci. 9, et al). "The Lord, the Almighty, will punish them on the Day of Judgment by putting fire and worms into their flesh, so that they cry out with pain unto all eternity" (Judith xvi. 17). The sinners in Gehenna will be filled with pain when God puts back the souls into the dead bodies on the Day of Judgment, according toIsa. xxxiii. 11 (Sanh. 108b).
Link: Jewish Encyclopedia Online
Note, scripture references are highlighted in blue.
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Encyclopedia Judaica:
Gehinnom (Heb. גֵּי בֶן־הִנֹּם, גֵּי בְנֵי הִנֹּם, גֵּיא בֶן־הִנֹּם, גֵּיא הִנֹּם; Gr. Γέεννα; "Valley of Ben-Hinnom, Valley of [the Son (s) of] Hinnom," Gehenna), a valley south of Jerusalem on one of the borders between the territories of Judah and Benjamin, between the Valley of *Rephaim and *En-Rogel (Josh. 15:8; 18:16). It is identified with Wadi er-Rababi.
…..During the time of the Monarchy, Gehinnom, at a place called Topheth, was the site of a cult which involved the burning of children (II Kings 23:10; Jer. 7:31; 32:35 et al.; ). Jeremiah repeatedly condemned this cult and predicted that on its account Topheth and the Valley of the Son of Hinnom would be called the Valley of the "Slaughter" (Jer. 19:5–6).
In Judaism the name Gehinnom is generally used as an appellation of the place of torment reserved for the wicked after death. The New Testament used the Greek form Gehenna in the same sense.
Gehinnom
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Talmud -Tractate Rosh Hashanah Chapter 1.
The school of Hillel says: . . . but as for Minim, [followers of Jesus] informers and disbelievers, who deny the Torah, or Resurrection, or separate themselves from the congregation, or who inspire their fellowmen with dread of them, or who sin and cause others to sin, as did Jeroboam the son of Nebat and his followers, they all descend to Gehenna, and are judged there from generation to generation, as it is said [Isa. lxvi. 24]:
"And they shall go forth and look upon the carcases of the men who have transgressed against Me; for their worm shall not die, neither shall their fire be quenched." Even when Gehenna will be destroyed, they will not be consumed, as it is written[Psalms, xlix. 15]: "And their forms wasteth away in the nether world," which the sages comment upon to mean that their forms shall endure even when the grave is no more.
Concerning them Hannah says [I Sam. ii. 10]: "The adversaries of the Lord shall be broken to pieces."
Link: Tract Rosh Hashana: Chapter I.