Note: I wrote the following to replace an inaccurate account on Wikipedia of Devadatta’s position in Theravāda Buddhism, which denied any canonical evidence for his standing, and blamed it on later, non-Canonical sources.
In Cullavagga section VII of the Vinayapiṭaka of the Theravādins which deals with schisms it is told how Devadatta went forth along with a number of the Buddha’s other relatives and clansmen. In the first year he attained psychic power, but made no supermundane achievement.
Looking round to see whom he could convince to honour him he decided to approach Prince Ajātasattu, the heir to the Magadhan throne. Having psychic power he assumed the form of a young boy clad in snakes and sat in the Prince’s lap, which very much impressed the prince, who became his disciple.
Ajātasattu began to send great offerings to Devadatta, and the latter became obsessed with his own worth, and began to have thoughts that it was he who should lead the Sangha, not the Buddha, and he didn’t desist even though this thought brought down his psychic powers.
When told about the offerings that Devadatta was receiving the Buddha remarked that all these gains were only going towards his destruction, just as a plantain or a bamboo is destroyed by its fruit.
Shortly thereafter Devadatta asked the Buddha to retire and let him take over the running of the Sangha. The Buddha retorted that he did not even let his trusted disciples Sāriputta or Moggallāna run the Sangha, much less one like him, who should be vomited like spittle, and he gave a special act of publicity about him, warning the monks that he had changed for the worse.
Seeing the danger in this Devadatta approached Prince Ajātasattu and encouraged him to kill his Father, the good King Bimbisāra, and meanwhile he would kill the Buddha. The King found out about his plan and gave over the Kingdom into the Prince’s control.
Ajātasattu then gave mercenaries to Devadatta who ordered them to kill the Buddha, and in an elaborate plan to cover his tracks he ordered other men to kill the killers, and more to kill them and so on, but when they approached the Buddha they were unable to carry out their orders, and were converted instead.
Devadatta then tried to kill the Buddha himself by throwing a rock at him from on high, while the Buddha was walking on the slopes of a mountain. As this also failed he decided to have the elephant Nāḷāgiri intoxicated and let him loose on the Buddha while he was on almsround. However, the power of the Buddha’s loving-kindness overcame the elephant.
Devadatta then decided to create a schism in the order, and collected a few monk friends, and demanded that the Buddha accede to the following rules for the monks: they should dwell all their lives in the forest, live entirely on alms obtained by begging, wear only robes made of discarded rags, dwell at the foot of a tree and abstain completely from fish and flesh.
The Buddha refused to make any of these compulsory, however, and Devadatta went round blaming him, saying that he was living in abudance and luxury. Devadatta then decided to create a schism and recite the training rules (pātimokkha) apart from the Buddha and his followers, with 500 newly ordained monks.
The Buddha sent his two Chief Disciples Sāriputta and Moggallāna to bring back the erring young monks. Devadatta thought they had come to join his Sangha, and asking Sāriputta to give a talk, fell asleep. Then the Chief Disciples persuaded the young monks to return to the Buddha.
The Buddha praised the Chief Disciples and blamed Devadatta saying that he was doomed to the Niraya Hell for his deeds, and it is reported that shortly thereafter he did in fact fall into Hell.
These verses are from the end of the same section of the Vinaya.
The Buddha then recited these verses:
Mā jātu koci lokasmiṁ pāpiccho udapajjatha,
Do not let anybody with wicked desires rise in the world,
Tad-amināpi jānātha: pāpicchānaṁ yathāgati.
Know him by this: the destiny of those who have wicked desires.
Paṇḍito ti samaññāto, bhāvitatto ti sammato,
Designated as a wise one, agreed upon as developed,
Jalaṁ va yasasā aṭṭhā Devadatto ti, me sutaṁ.
Devadatta stood there blazing forth with fame, or so I have heard.
So pamādaṁ anuciṇṇo āsajja naṁ Tathāgataṁ,
(But) through practising heedlessness, he attacked the Realised One,
Avīcinirayaṁ patto catudvāraṁ bhayānakaṁ.
And he attained the unceasing four-doored, fearful Niraya Hell.
Aduṭṭhassa hi yo dubbhe pāpakammaṁ akrubbato,
The treacherous one (who attacks) the innocent, who did no bad,
Tam-eva pāpaṁ phusati: duṭṭhacittaṁ anādaraṁ.
Himself attains what is wicked: a corrupt mind and disrespect.
Samuddaṁ visakumbhena yo maññeyya padūsituṁ,
He who could think to defile the ocean with a pot of poison,
Na so tena padūseyya, bhesmā hi udadhī mahā.
Can not defile it with that thing, for the great ocean is awesome.
Evam-eva Tathāgataṁ yo vādenupahiṁsati,
Even so he who would injure the Realised One with his words,
Samaggataṁ santacittaṁ, vādo tamhi na rūhati.
The peaceful one, with peaceful mind, that word will not have an effect.
Tādisaṁ mittaṁ krubbetha, tañ-ca sevetha paṇḍito,
He should make a friend of such, and associate with the wise one,
Yassa maggānugo bhikkhu, khayaṁ dukkhassa pāpuṇe ti.
The monk who goes along his path will attain the end of suffering.