"Whatever person, even unasked,

Speaks to others of his own morality and observances...

Adept ones say his is an ignoble way.

But a mendicant at peace, with self completely blown out,

Not boasting about his morality saying, “I am like this,”

For whom there are no distinguished positions at all in the world –

Adept ones say that his is a noble way."

yo attano sīlavatāni jantu

anānupuṭṭhova paresa pāvā...

yo ātumānaṁ sayameva pāvā

santo ca bhikkhu abhinibbutatto

itihanti sīlesu akatthamāno

tamariyadhammaṁ kusalā vadanti

yassussadā natthi kuhiñci loke

What is the Aṭṭhakavagga?

The Aṭṭhakavagga is the fourth chapter of an ancient collection of Buddhist scriptures known as the Sutta Nipāta. Although it is only a single chapter of a larger work, there is good evidence suggesting that the Aṭṭhakavagga existed in its own right prior to the compilation of the Sutta Nipāta, and that it was much better known and more influential in ancient times than it is today. This lapse into relative obscurity is unfortunate, as the Aṭṭhakavagga contains invaluable information for anyone wishing to better understand the earliest teachings of Buddhism, and also for anyone seeking the way of wisdom."

https://pathpress.wordpress.com/wp-content/uploads/2012/06/ppts1-atthakavagga2.pdf

Some scholars regard the Aṭṭhakavagga and the Pārāyanavagga as being considerably earlier in composition than the bulk of the canon, and as revealing an earlier form of Buddhism.