Short answer. Less than the tradition built on him, and in different words. The term he uses is Gehenna, eleven times across Matthew, Mark and Luke, and Gehenna is a real ravine outside Jerusalem, the Valley of Hinnom. He never describes the furnished afterlife of later Christian imagination, and he never says Satan rules it. The whole weight of the eternal-conscious-torment reading rests on one verse, Matthew 25:46, and it turns on a Greek adjective that does not settle the question in either direction.
Tier note: the word counts and the identification of Gehenna are bedrock and checkable in any concordance. What those sayings mean is contested, and this page does not pretend otherwise. It gives the strongest reading on each side and marks where the evidence stops.
The word he actually used
The Greek geenna appears twelve times in the New Testament. Eleven are on the lips of Jesus, in Matthew 5:22, 5:29, 5:30, 10:28, 18:9, 23:15 and 23:33; Mark 9:43, 9:45 and 9:47; and Luke 12:5. The twelfth is James 3:6. That is the entire New Testament usage.
It is a transliteration of Hebrew ge hinnom, the Valley of Hinnom, a real ravine on the southern edge of Jerusalem. It carried a specific and terrible history: the Hebrew Bible associates it with child sacrifice under Ahaz and Manasseh, and Jeremiah curses it by name and renames it the Valley of Slaughter. By the first century it had become a byword for the place of final judgment.
The point is not that Jesus meant only a garbage dump, which is a popular claim that outruns the evidence. It is that he was reaching for an image his hearers already had, a cursed valley with a name and a location, and not for the architecture later readers bring to the word “hell.” See Gehenna vs Sheol vs Hades.
The one verse that carries the weight
Matthew 25:46 closes the parable of the sheep and the goats: these will go away into aionios kolasis, but the righteous into aionios life. This is the load-bearing text, and notice the structure. The same adjective governs both halves.
That parallel is real, and it cuts in both directions, which is why honest readers on each side have to live with it. If aionios means endless, then the punishment is endless and so is the life. If it means “belonging to the age to come,” which is a defensible rendering of an adjective built on aiōn, age, then both are age-belonging and the duration is simply not what the sentence is about. You cannot take it one way on the left and the other way on the right.
The majority of scholars read aionios as everlasting. A real minority, led by Ilaria Ramelli and David Bentley Hart, reads it as age-belonging. The Greek does not settle it in either direction, and anyone telling you the word alone decides the question is selling something. See What does aionios mean?.
The saying that cuts against eternal torment
Matthew 10:28 is rarely quoted by either side, and it is the most interesting of the eleven: fear the one who can destroy both soul and body in Gehenna. The verb is destruction, not perpetual torment, and it is applied to the soul as well as the body.
Read plainly, that is closer to annihilation than to endless conscious suffering, and it is Jesus's own sentence rather than a later inference. It does not settle the matter either, because a reader can take “destroy” as ruin rather than extinction. But a tradition that teaches the soul is inherently immortal and therefore must suffer forever has to do something with a saying in which the soul is the thing that can be destroyed. See What is annihilationism? and Is the immortal soul Greek or Hebrew?.
The saying that cuts the other way
Fairness requires the reverse. Mark 9:48 describes Gehenna as the place “where their worm does not die and the fire is not quenched,” which is about as severe as language gets, and Matthew 25:41 speaks of a fire prepared for the devil and his angels. Anyone arguing that Jesus was soft on judgment is not reading him.
The honest complication runs underneath: Mark 9:48 is a direct quotation of Isaiah 66:24, and in Isaiah the undying worm and unquenchable fire are consuming corpses, not living sufferers. That is a fact about the source text rather than a proof about the quotation, and it belongs on the page in either case.
What he did not say
He never says Satan rules Gehenna. Not once, and neither does anyone else in the New Testament. Satan as sovereign of hell, presiding over the damned, is Dante and Milton, arriving more than a millennium later. In the New Testament the adversary is the one judged, not the one judging.
He gives no description of the place. There are no levels, no demons with instruments, no catalogue of punishments matched to sins. Every image of that kind comes from later apocalyptic literature such as the Apocalypse of Peter, and then from medieval poetry.
He does not use the word “hell.” That is an English word doing the work of at least three different ones. In the Hebrew Bible Sheol is the grave-world everyone goes to, and the King James Version renders it “grave” thirty-one times and “hell” thirty-one times, sorting essentially by whether the translators thought the person deserved it. The doctrine is partly living in the translation.
What this does and does not establish
It establishes that the vocabulary is narrower and more concrete than the tradition built on it, that the eternal-conscious-torment reading rests on a single verse whose key adjective is genuinely contested, and that at least one of Jesus's own sayings points toward destruction rather than endless torment.
It does not establish that Jesus taught universal restoration. He did not, at least not in these eleven sayings, and a page claiming otherwise would be doing in the other direction exactly what it accuses the tradition of doing. What the early church did with the question is a separate matter, and there the answer is genuinely surprising: restorationism was a live and mainstream patristic option for centuries. See What is apokatastasis? and Is hell eternal?.
Common questions
How many times did Jesus talk about hell?
He uses the word Gehenna eleven times: Matthew 5:22, 5:29, 5:30, 10:28, 18:9, 23:15, 23:33; Mark 9:43, 9:45, 9:47; and Luke 12:5. The word appears twelve times in the New Testament in total, the remaining instance being James 3:6. He also speaks of judgment in other terms and images, but Gehenna is the specific word usually translated “hell.”
What is Gehenna?
A real ravine on the southern edge of Jerusalem, the Valley of Hinnom, in Hebrew ge hinnom. The Hebrew Bible associates it with child sacrifice under Ahaz and Manasseh, and Jeremiah curses it by name and renames it the Valley of Slaughter. By the first century it had become an image for the place of final judgment. The popular claim that it was simply the city rubbish dump in Jesus's day outruns the evidence and is not needed for the point.
Does Matthew 25:46 prove hell is eternal?
It is the strongest text for that reading and it does not settle it. The verse contrasts aionios punishment with aionios life using the same adjective for both, so whatever it means, it means the same on both sides. If it means endless, both are endless. If it means belonging to the age to come, which is a defensible rendering of an adjective built on aiōn, age, then duration is not what the sentence is asserting. Most scholars read it as everlasting; a real minority including Ilaria Ramelli and David Bentley Hart does not. The Greek alone decides it for no one.
Did Jesus say Satan rules hell?
No, and neither does any other New Testament writer. Satan as the ruler of hell presiding over the damned is a later literary development, reaching its familiar form in Dante and Milton more than a thousand years afterward. In the New Testament the adversary is among the judged rather than the judge.
Is hell in the Old Testament?
Not as a place of eternal conscious torment. The Hebrew word is Sheol, the shadowy grave-world where everyone goes, righteous and wicked alike, as when Jacob expects to go down to Sheol mourning in Genesis 37:35. The King James Version translates the same word “grave” thirty-one times and “hell” thirty-one times, largely according to whether the person in question seemed to deserve it, which is a translator's theology showing through the text rather than a distinction present in the Hebrew.
So did Jesus believe in hell or not?
He believed in judgment, said so severely, and used a concrete image his hearers knew. What the evidence does not support is reading the full later doctrine back into his words, because the vocabulary is narrower, the descriptions are absent, the ruler is absent, and the one verse carrying the eternal-torment weight hangs on a contested adjective. The honest position is that his language is severe and its duration is unresolved, and that the early church itself did not treat the question as closed.
Sources
Matthew 5:22, 5:29-30, 10:28, 18:9, 23:15, 23:33, 25:41, 25:46; Mark 9:43-48; Luke 12:5; James 3:6; Isaiah 66:24; Jeremiah 7:31-32, 19:1-6; 2 Kings 16:3, 21:6; Genesis 37:35. Ilaria L. E. Ramelli, The Christian Doctrine of Apokatastasis; David Bentley Hart, The New Testament: A Translation; Joachim Jeremias, geenna in TDNT; Bart D. Ehrman, Heaven and Hell: A History of the Afterlife (2020).