Later, Upāli and his pupils became known as vinayadharas (Pāli; 'custodians of the vinaya'), who preserved the monastic discipline after the Buddha's parinibbāna (Sanskrit: parinirvāṇa; passing into final Nirvana).

The technical conversations about vinaya between the Buddha and Upāli were recorded in the Pāli and Sarvāstivāda traditions and have been suggested as an important subject of study for modern-day ethics in American Buddhism.

[3][4] He was from an artisan class family in service to the Sakya princes in Kapilavatthu (Sanskrit: Śakya; Kapilavastu) and, according to the Mahāvastu, to the Buddha.

Buddhologist André Bareau argues that this story is ancient, because it precedes the tradition of art depictions of the Buddha with curly hair, and the glorification of Upāli as an adult.

According to the Mahāvastu, the Pāli Cullavagga and the texts of discipline of the Mūlasarvāstivāda order, when the princes left home to become monks, Upāli followed them.

[7] Several variations on the story of Upāli's ordination exist, but all of them emphasize that his status in the saṅgha (Sanskrit: saṃgha; monastic community) was independent of his caste origin.

[9] It became widely known that the Sakyans had their barber ordained before them to humble their pride,[10] as the Buddha related a Jātaka tale that the king and advisers had bowed for Upāli in a previous life, too.

Rhys Davids noted that Upāli was the "striking proof of the reality of the effect produced by Gautama's disregard of the supposed importance of class".

Schumann also raises Upāli as an example of the general rule that "in no case did ... humble origins prevent a monk from becoming prominent in the Order".

[14] Historian Sangh Sen Singh argues that Upāli could have been the leader of the saṅgha after the Buddha's parinibbāna instead of Mahākassapa (Sanskrit: parinirvāṇa, Mahākāśyapa).

But the fact that he was from humble origins effectively prevented this, as many of the Buddhist devotees at the time might have objected to his leadership position.

Pāli scholar Gunapala Malalasekera argued that the Buddha wanted Upāli to learn both meditation and Buddhist doctrine, and a life in the forest would have provided him with only the former.

[5] 5th-century commentator Buddhaghosa stated that Upāli drew up instructions and explanatory notes for monks dealing with disciplinary matters.

[36] At the council, Upāli was asked to recite the vinaya of monks and nuns, including the pāṭimokkha,[37], and the Vinayapiṭaka (collection of texts on monastic discipline) was compiled based thereon.

[42] Sixteen years after the Buddha's passing away, Upāli ordained a pupil called Dāsaka, who would become his successor with regard to expertise in monastic discipline.

[35] In some Buddhist texts, an explanation is offered why a low-caste born monk would have such a central role in developing monastic law.

[19][44] Despite Upāli's previous lives as a king, he was born as a low caste barber in the time of Gotama Buddha.

This is also explained in an Apadāna story: in a previous life, Upāli insulted a paccekabuddha (Sanskrit: pratyekabuddha; a type of Buddha).

[19][44] Upāli was the focus of worship in ancient and medieval India and was regarded as the "patron saint" of monks who specialize in the vinaya.

In 4th–5th-century Ceylon, they then came to be associated with a lineage of such masters, because of the influence of Buddhaghosa, who established Upāli and the other vinayadharas as an important characteristic of the Mahāvihāra tradition.

Chinese sources say that Upāli and his successors had a custom to insert a dot in a manuscript marking each year after the First Council.

The sources claim that each of successors continued this tradition, up until 489 CE, when the Sarvāstivāda scholar Saṃghabhadra entered the last dot in the manuscript.

Still, data pertaining to the vinayadharas is used to support theories regarding the dating of the Buddha's life and death, such as the one proposed by Indologist Richard Gombrich.

In 7th-century China, the Vinaya or Nan-shan School was founded by the monks Ku-hsin and Tao-hsüan, seen as a continuation of Upāli's lineage.

[57] In the Pāli tradition, numerous discourses show the Buddha and Upāli discussing matters of monastic discipline, including the legality of decision-making and assemblies, and the system of giving warnings and probation.

[19] Religion scholar Charles Prebish has named the Upalipariprccha as one of twenty-two texts worthy of study and practice, in order to develop American Buddhist ethics.