大唐西域記 5.24-25

To the north of this stûpa are the ruins of a sanghârâma. here that Srilabdha (Shi-li-lo-to), a master of sastras belonging to the Sautrantika school, composed the Vibhasha Sastra of that school. To the south-west of the city 5 or 6 li, in an extensive grove of Amra trees, is an old sangharama; this is where Asanga Bodhisattva pursued his studies and directed the men of the age. Asanga Bodhisattva went up by night to the palace of Maitreya Bodhisattva, and there received the Yogacharya Sastra, the Mahayana Sutralankaratika, the Madhyanta Vibhanga Sastra, &c., and afterwards declared these to the great congregation, in their deep principles.

North-west of the Amra grove about a hundred paces is a stupa containing relics of the hair and nails of Tathagata. By its side are some old foundation walls. This is where Vasubandhu Bodhisattva descended from the Tushita heaven and beheld Asanga Bodhisattva. Asanga Bodhisattva was a man of Gandhara. He was born in the middle of the thousand years following the departure of Buddha from the world; and possessed of deep spiritual insight, he soon acquired a knowledge of the doctrine (of Buddha). He became a professed disciple, and attached himself to the school of the Mahisasakas, but afterwards altered his views and embraced the teaching of the Great Vehicle. His brother, Vasubandhu Bodhisattva, belonged to the school of the Sarvastivadins, and had inherited a wide fame, with a strong intelligence and penetrating wisdom and remarkable acumen. The disciple was Buddhasimha, a man whose secret conduct was unfathomable, of high talent and wide renown. These two or three worthies had often talked together in this way: "We all are engaged in framing our conduct so as to enjoy the presence of Maitreya after death. Whoever of us first dies and obtains the condition (of life), let him come and communicate it to us, that we may know his arrival there."