score:8
It's fairly clear that three times was a social convention for crossing some sort of line; either that or just a convention of the Buddha. See also DN 3:
‘Reverend Gotama, there are four castes: the Khattiyas, the Brahmins, the merchants and the artisans. And of these four castes three — the Khattiyas, the merchants and the artisans — are entirely subservient to the Brahmins. With regard to this, it is not proper that they should not pay homage to the Brahmins.’ This was the third time Ambattha accused the Sakyans of being menials.
Then the Lord thought: ‘This young man goes too far in abusing the Sakyans."
and
Again Ambattha remained silent, and the Lord said: ‘Answer me now, Ambattha, this is not a time for silence. Whoever, Ambattha, does not answer a fundamental question put to him by a Tathāgata by the third asking has his head split into seven pieces.’
Walshe, the translator of the above, gives as a note for the second passage, "A curious threat that (as RD observes) never comes to anything, and is of course pre-Buddhist."
Not sure if the "third time" is also pre-Buddhist, but again, it appears to be some sort of line in the sand for the Buddha at least.
Upvote:2
No one knows. It was probably just a social convention of the time.
Upvote:3
I always assumed it was a skillful means of getting the person to go away as soon as possible. Not relenting after two rebukes, at that point, the Buddha assuming this person was not getting the hint, did what was necessary to return to seclusion.
Although I don't believe I have ever seen any mention of this in the Pali Canon, so this is only conjecture. Conjecture based on the Buddha's teaching of right speech and on the virtue of seclusion.
He avoids idle chatter and abstains from it. He speaks at the right time, in accordance with facts, speaks what is useful, speaks of the Dhamma and the discipline; his speech is like a treasure, uttered at the right moment, accompanied by reason, moderate and full of sense. – AN 10:176
In this way, one can see that the Buddha was purposeful in the manner in which he spoke, and as such would not be doing so simply as a cultural norm.