I believe there are warnings about hell in the Old Testament. Sheol is not a neutral place, but the place where the wicked are sent. The warnings about Sheol would not be warnings if Sheol was simply a neutral place where all dead souls go.
I’ve probably argued before that Sheol is merely the place of the dead, but having looked through the Old Testament texts again, I think that Alex may have half a point. Here I have roughly sorted much of the Old Testament data under what seem to me to be the most useful headings and then added a summary definition. My suggestion, briefly, is that while Sheol is in principle the place of the dead, the imagery of going down to Sheol carries the particular connotation of an unfortunate, wretched or god-forsaken death.
Sheol is the place of the dead
Korah and his family do not suffer the fate of all humanity; they are swallowed up by the earth on account of their rebellion and “go down into Sheol” (Num. 16:29-30). But the novelty is not that they go to Sheol; it is that they go down to Sheol alive. This passage effectively excludes the possibility that Sheol is reserved for the wicked. ;Ecclesiastes assumes that all people go to Sheol and argues only that they should make the most of life while they can (Eccl. 9:10).
The identification of Sheol with death and the grave is often reinforced by synonymous parallelism. For example, David says:
The cords of death encompassed me; the torrents of destruction assailed me; the cords of Sheol entangled me; the snares of death confronted me. (Ps. 18:4–5; 2 Sam. 22:5-6; cf. Ps. 116:3)
Not to be abandoned to Sheol is not to see corruption (Ps. 16:10). Those who have “foolish confidence” in wealth are like sheep “appointed for Sheol”; “death shall be their shepherd”, and their “form shall be consumed in Sheol” (Ps. 49:13-14). For Job to descend into Sheol is to descend into the dust (Job 17:16). The person who enters the house of the “woman Folly” does not “know that the dead are there, that her guests are in the depths of Sheol” (Prov. 9:18). Isaiah accuses the leadership in Jerusalem of having made a “covenant with death”, an “agreement with Sheol” (Is. 28:15, 18). Hosea has God ask:
Shall I ransom them from the power of Sheol? Shall I redeem them from Death? O Death, where are your plagues? O Sheol, where is your sting? (Hos. 13:14)
Sheol is equivalent to death and physical decay in these statements; it is never more than death.
The opposite of Sheol is life
Sheol is never contrasted with an alternative blessed home for the righteous dead. The antithesis to Sheol is life. Hannah proclaims, “The Lord kills and brings to life; he brings down to Sheol and raises up” (1 Sam. 2:6). David celebrates the fact that he has been saved from his enemies and from death and has been restored to life (Ps. 30:3). The soteriology is straightforward: he might have died but instead he is alive. Jonah calls for help “out of the belly of Sheol” (Jon. 2:2): his desire is not to escape hell but to escape death and live. The feet of the “forbidden woman” or adulteress “go down to death; her steps follow the path to Sheol; she does not ponder the path of life; her ways wander, and she does not know it” (Prov. 5:5-6). Sexual immorality leads to death rather than to life.
Going down to Sheol as a wretched death
Jacob fears that he will go down to Sheol mourning the death of his son (Gen. 37:35; 42:38; 44:29, 31). He clearly does not expect to go to hell to suffer eternal conscious torment, but he views such a death as unfortunate, perhaps even as a sign of divine judgment: a righteous man should be gathered to his fathers (Gen. 47:30; 49:29, 33), or gathered to his grave in peace (cf. 2 Kgs. 22:20). David tells Solomon that Joab should not be allowed to go down to Sheol in peace—that is, he should suffer the death of the wicked, not the righteous (1 Kgs. 2:6, 9). Job, however, regrets the fact that the wicked “spend their days in prosperity, and in peace they go down to Sheol” (Job 21:13). When the righteous pray that God will keep them from Sheol, it is typically when their lives are threatened by an enemy or illness.
There is no relationship with God in Sheol
David prays to be kept alive because “in death there is no remembrance of you; in Sheol who will give you praise?” (Ps. 6:5; cf. 88:10). Hezekiah believed that he was about to leave the land of the living and was “consigned to the gates of Sheol” (Is. 38:10). Death is to be avoided because there is no praise of God in Sheol, and those who go down to the pit do not hope for God’s faithfulness; but the two options open to Hezekiah are simply life and death, not heaven and hell. “The living, the living, he thanks you, as I do this day; the father makes known to the children your faithfulness” (Is. 38:18-19).
The wicked go down to Sheol
The hope of the righteous is that the wicked will go down to Sheol: “Let death steal over them; let them go down to Sheol alive” (Ps. 55:15; cf. 31:17). When Judah is invaded, Sheol will enlarge its appetite and the greedy, unjust “nobility of Jerusalem and her multitude will go down” (Is. 5:14). The king of Babylon will be greeted by the “shades” of dead kings when he is brought down to Sheol (Is, 14:9, 11, 15). Whole nations will be defeated by God and brought down to Sheol because of their antipathy towards Israel (Ps. 9:17; Ezek. 31:15-17; 32:21). The basic argument is not that the wicked will suffer a punishment beyond death but that their wealth and political strength in this life will ultimately be of no avail. No mention is made of eternal conscious torment.
Sheol is the underworld, the place where all the dead go. But the language of “going down to Sheol” in the Old Testament appears to carry the specific negative connotation of suffering an unfortunate, wretched or god-forsaken death. So on the one hand, the righteous hope to avoid the sort of death that might be described in these terms, not least because there is no further relationship with God in Sheol; and on the other, the hope is frequently expressed that the wicked will go down to Sheol as a matter of moral justice. The existence of the dead in Sheol, however, is shadowy and largely poetic, and there is no suggestion that the “shades” of the dead are being actively punished there.
Alex argues that “there is continuity between Old and New Testament doctrine”. He is right. But it seems to me an unavoidable conclusion exegetically that both the Jewish scriptures and Jesus teach that the final end of sinful humanity is death.