Concerning the need of keeping regular days
for retirement from worldly labours and religious instruction,
the king went to the Blessed One and said:
"The Parivrajaka, who belong to the Titthiya school,
prosper and gain adherents because they keep the eighth day
and also the fourteenth or fifteenth day of each half-month.
Would it not be advisable for the reverend brethren of the Sangha
also to assemble on days duly appointed for that purpose?" [2]

And the Blessed One commanded the bhikkhu to assemble on the eighth day
and also on the fourteenth or fifteenth day of each half-month,
and to devote these days to religious exercises. [3]

A bhikkhu duly appointed should address the congregation and espound the Dharma.
He should exhort the people to walk in the eightfold path of righteousness;
he should comfort them in the vicissitudes of life
and gladden them with the bliss of the fruit of good deeds.
Thus the brethren should keep the Uposatha. [4]

Now the bhikkhus, in obedience to the rule laid down by the Blessed One,
assembled in the vihara on the day appointed,
and the people went to hear the Dharma,
but they were greatly disappointed,
for the bhikkhus remained silent
and delivered no discourse. [5]

When the Blessed One heard of it,
he ordered the bhikkhus to recite the Patimokkha,
which is a ceremony of disburdening the conscience;
and he commanded them to make confession of their trespasses
so as to receive the absolution of the order. [6]

A fault, if there be one, should be confessed
by the bhikkhu who remembers it and desires to be cleansed.
For a fault, when confessed, shall be light on him. [7]

And the Blessed One said:
"The Patimokkha must be recited in this way: [8]

"Let a competent and venerable bhikkhu
make the following proclamation to the Sangha:
'May the Sangha hear me! To-day is Uposatha,
the eighth, or the fourteenth or fifteenth day of the half-month.
If the Sangha is ready, let the Sangha hold the Uposatha service
and recite the Patimokkha. I will recite the Patimokkha.' [9]

"And the bhikkhus shall reply:
'We hear it well and we concentrate well our minds on it, all of us.' [10]

"Then the officiating bhikkhu shall continue:
'Let him who has committed an offence, confess it;
if there be no offence, let all remain silent;
from your being silent I shall understand
that the reverend brethren are free from offences. [11]

"'As a single person who has been asked a question answers it,
so also, if before an assembly like this
a question is solemnly proclaimed three times, an answer is expected:
if a bhikkhu, after a threefold proclamation,
does not confess an existing offence which he remembers,
he commits an intentional falsehood. [12]

"'Now, reverend brethren, an intentional falsehood
has been declared an impeditment by the Blessed One.
Therefore, if an offence has been committed by a bhikkhu
who remembers it and desires to become pure,
the offence should be confessed by the bhikkhu;
and when it has been confessed, it is treated duly.'" [13]