This is how I heard from the Blessed One. At one time the Blessed One was staying in the city of Uruvelā on the bank of the river Nerañjarā at the foot of the Ajapāla Banyan Tree, having just realised supreme enlightenment. There, the Blessed One was sitting cross legged for seven days straight experiencing the peace of liberation.
At the end of those seven days, the Blessed One emerged from that concentration. Then a certain Brāhmin from the clan of Huhuṁka went to the Blessed One. He exchanged polite and friendly greetings with the Buddha and stood to one side. as he was standing there the Brāhmin asked the Blessed One, “Master Gotama, how does one become a Brāhmin? What are the qualities that make one a Brāhmin?”
Then, the Blessed One who realised the true nature as it really is spoke the following inspired verse,
Any liberated one who has discarded all evil, not conceited, free from stains of defilements, has a controlled mind, has achieved the culmination of true knowledge, has completed the path to ultimate freedom, Nibbāna, and is not disturbed by any object in the world is called, the Brāhmin.