Personalities of the Buddhist Suttas
DPPN: He belonged to a brahmin family of Donavatthu near Kapilavatthu. His mother was Mantani, sister of Annakondanna. Annakondanna ... ordained Punna ... Punna remained in Kapilavatthu, intent on his practices, and soon after became an arahant. He gathered round him five hundred clansmen who all became monks, and he taught them the ten bases of discourse, which he himself had learnt, and they became arahants. When they wished to visit the Buddha, Punna sent them on in advance to Rajagaha, asking them to pay homage to the Buddha in his name. Later, when the Buddha came from Rajagaha to Savatthi, Punna visited him and was taught the Dhamma in the Buddha's own Gandhakuti - The name given to the special apartment occupied by the Buddha at the Jetavana monastery.
--Sariputta, hearing of the fame of Punna, wished to meet him, and went to Andhavana, where Punna was spending his siesta. Sariputta questioned him on the seven acts of purity, and Punna answered him. The two monks found great joy in each others words.
From The Psalms of the Early Buddhists; Punna's declaration of arahantship:
Aye with the good consort, with them
Who know, who understand, who see the Good
Great is the Good and deep and hard to see,
Subtle and delicately fine, to which
The wise and brave do penetrate, e'en they
Who strenuous live and lofty vision gain.