On the Authenticity of Abhidhamma and Commentaries - Tibetan and Chinese sources
These are Accounts from Tibetan and Chinese sources regarding the first council, if anyone is looking for a confirmation outside of Theravada tradition.
(I coudn’t get access to the original sources yet.)
“Geiger’s introduction to his translation of the ‘Mahavamsa’ (PTS)”:
"Among the Northern Buddhist sources dealing with the first Council I mention the Mahavastu. Here, in agreement with the southern tradition Kasyapa is given as the originator of the coucil, the number of the bhiksus taking part is stated to be 500 and the place the aptaparna grotto near Rajagrha.
"There is, besides, an account in the second volume of the Dulva, the Tibetan Vinaya of the Sarvastivadin sect. The fixing of the canon took place, according to this source, in the following order: 1) Dharma, by Ananda; 2)Vinaya, by Upali; 3)Matrka (i.e.Abhidarma) by Mahakasyapa himself.…
“Fa-hian and Hiuen-thsang also mention the First Council. The former gives the number of the bhiksus a 500, the latter as 1,000; the former speaks in a general way of ‘a collection of sacred books’, the latter expressly mentions also the redaction of the Abhidharma by Mahakasyapa.”
Norman, K.R. (1983) Pali Literature , p. 119. :
(Included in Wikipedia as well)
There is no direct evidence that any commentarial material was in fact recited at the first council, but there is clear evidence that some parts of the commentaries are very old, perhaps even going back to the time of the Buddha, because they afford parallels with texts which are regarded as canonical by other sects, and must therefore pre-date the schisms between the sects. As has already been noted, some canonical texts include commentarial passages, while the existence of the Old Commentary in the Vinaya-pitaka and the canonical status of the Niddesa prove that some sort of exegesis was felt to be needed at a very early stage of Buddhism.