The seventh sutta of the Uraga Vagga of the Suttanipāta. It was taught at Sāvatthi to the brahmin Aggikabhāradvāja (it is thus also called the Aggikabhāradvāja Sutta, SNA.174), who reviled the Buddha, calling him outcaste (vasala) when the Buddha went to his house for alms.
The Buddha replied that the brahmin knew neither the meaning of outcaste, nor what makes a man such. At the request of the brahmin he taught this sutta, the burden of which is that it is not by birth that one is an outcaste or a brahmaṇa, but by one’s deeds (SN., pp.21 f).
The Sutta is also included in the Paritta suttas (q.v.)