Mahavagga, Khandaka 2, Chapter 1

1. At that time the blessed Buddha dwelt near Rājagaha, on the Gijjhakūṭa mountain ('the Vulture's Peak'). At that time the Paribbājakas belonging to Titthiya schools assembled on the fourteenth, fifteenth, and eighth day of each half month^[1] and recited their Dhamma. The people went to them in order to hear the Dhamma. They were filled with favour towards, and were filled with faith in, the Paribbājakas belonging to Titthiya schools; the Paribbājakas belonging to Titthiya schools gained adherents.

2. Now when the Māgadha king Seniya Bimbisāra was alone, and had retired into solitude, the following consideration presented itself to his mind: 'The Paribbājakas belonging to Titthiya schools assemble now on the fourteenth, fifteenth, and eighth day of each half month and recite their Dhamma. The people go to them in order to hear the Dhamma. They are filled with favour towards, and are filled with faith in, the Paribbājakas who belong to Titthiya schools; the Paribbājakas who belong to Titthiya schools gain adherents. What if the reverend ones (the Buddhist Bhikkhus) were to assemble also on the fourteenth, fifteenth, and eighth clay of each half month.'

3. Then the Māgadha king Seniya Bimbisāra went to the place where the Blessed One was; having approached him and having respectfully saluted the Blessed One, he sat clown near him. Sitting near him the Māgadha king Seniya Bimbisāra said to the Blessed One: 'Lord, when I was alone and had retired into solitude, the following consideration presented itself to my mind: "The Paribbājakas, &c.; what if the reverend ones were to assemble also on the fourteenth, fifteenth, and eighth clay of each half month." Well, Lord, let the reverend ones assemble also on the fourteenth, fifteenth, and eighth clay of each half month.'

4. Then the Blessed One taught, incited, animated, and gladdened the Māgadha king Seniya Bimbisāra by religious discourse; and the Māgadha king Seniya Bimbisāra, having been taught and gladdened by the Blessed One by religious discourse, rose from his seat, respectfully saluted the Blessed One, passed round him with his right side towards him, and went away.

In consequence of that and on this occasion the Blessed One, after having delivered a religious discourse, thus addressed the Bhikkhus: 'I prescribe, O Bhikkhus, that you assemble on the fourteenth, fifteenth, and eighth clay of each month.'

Footnotes and references:

[1]:

One should be inclined to understand that the Paribbājakas assembled twice each half month, on the eighth day of the pakkha and on the fourteenth or fifteenth day, according to the different length of the pakkha. However, chap. 4 makes it probable that not two days in each pakkha are to be understood, but three. Compare, however, the remark of Buddhaghosa, quoted in the note on chap. 34. 1.