Day 13 covers all of Chapter 8, The Assurance of Future Buddhahood of the Five Hundred Disciples.

Having last month heard the Pūrṇa’s desire, we consider Śākyamuni’s praise for Pūrṇa.

Thereupon the Buddha said to the bhikṣus:

“Do you see this Pūrṇa, the son of Maitrāyanī? I always praise him, saying that he is the most excellent expounder of the Dharma. I also praise him for his various merits. He strenuously protects my teachings, and helps me propagate them. He shows the Way to the four kinds of devotees, teaches them, benefits them and causes them to rejoice. He explains my right teachings perfectly, and gives great benefits to those who are performing brahma practices’ with him. No one except the Tathāgata excels him in eloquence. Do not say that he protects only my teachings and helps me propagate them! In his previous existence he also protected the right teachings of nine thousand million Buddhas and helped them propagate their teachings. Under those Buddhas also he was the most excellent expounder of the Dharma. He clearly understood the truth of the Void expounded by those Buddhas, and obtained the four kinds of unhindered eloquence. He always expounded the Dharma clearly and purely, with no doubtfulness. Although he had the supernatural powers of Bodhisattvas, he performed brahma practices throughout his previous existence. Therefore, the people of the world of the Buddha [under whom he performed brahma practices] thought that he was a Śrāvaka. He benefited many hundreds of thousands of living beings with this expedient, and also caused innumerable, asaṃkhya people to aspire for Anuttara-samyak-saṃbodhi. He did the work of the Buddha, that is, taught all living beings so that the world of the Buddha might be purified.

The Introduction to the Lotus Sūtra offers this about Pūrṇa:

Among the Buddha’s many followers, ten were outstanding. Each was famous for possessing a particular talent which excelled all others. For example, Sariputra was the wisest; Maha-Kasyapa was known for his good practices; Maha-Maudgalyayana was famed for his supernatural powers; Purna was the best preacher, distinguished for his eloquence. This meant that he was more than just a master of rhetoric and silvery words; he could preach with such clarity that through him people could understand the Buddha’s deep teachings, and free themselves from sufferings.