<p>Recent studies have revealed that the foundation of Mahāyāna Buddhism in India was internal to each branch of Buddhism. If each school had its own Mahāyāna sūtras, they would be expected to have been transformed and diversified according to the characteris­tics of each school. In this regard it is possible that the language of the Mahāyāna sūtras （Sanskrit, Prākrit, etc.） may have been linked to the scriptural language unique to each school. This paper deals with the case of the Pūrvaśaila school in order to explore this possibility.</p><p>M. D. Eckel pointed out that Bhāviveka’s Tarkajvālā chapter 4 quotes a passage from the Brahmaviśeṣacintiparipṛcchā （= BP） and refers it as a Bodhisattvapiṭaka of the Pūrvaśaila school. The passage has now been recovered from chapter 1 of Abhayakaragup­ta’s Munimatālaṃkāra （fol. 9r1） and was found to be written in Prākrit. From this we learn the following two points: （1） The Bodhisattvapiṭaka is one of the Seven Piṭakas of this school, so the Mahāyāna sūtras were included in their scriptures, and （2） there are Sanskrit fragments of the BP apart from this, but this school chose to transmit a Prākrit version.</p><p>What about the language of the Āgama scriptures of the Pūrvaśaila school? P. Harrison reports two verses from the Lokānuvartanāsūtra, which Candrakīrti cites as the āgama­sūtra of the Pūrvaśaila school. They are written in Prākrit and linguistically close to the Prākrit version of the BP, if not the same. Thus, it is suggested that in the case of the Pūrvaśaila school, the scriptural language of the Āgama and Mahāyāna scriptures may have been unified in Prākrit. The inclusion of Prākrit Mahāyāna sūtras in the scriptures of Pūrvaśaila is also referred to by Avalokitavrata.</p><p>The correlation between the above-mentioned scriptural languages can be suggested by cases such as the Dharmaguptaka school, which transmitted Āgama and Mahāyāna scriptures in Gandhāra, but it cannot be generalized to all schools in all periods. For example, the Abhayagiri and Jetavana schools of the Theravāda tradition probably transmitted their Āgamas in Pāli and Mahāyāna sūtras in Sanskrit, so the languages of Āgama and Mahāyāna scriptures are different. On the other hand, the Sarvāstivādin school used Sanskrit for their Āgama scriptures. If there were Mahāyāna monks in this school, it is possible that they transmitted Mahāyāna sūtras in Sanskrit as well. If so, it is possible that some of the Mahāyāna sūtras in Sanskrit available to us today may have originated in the Sarvāstivāda school （aside from Sanskritized Mahāyāna sūtras of other schools）. </p><p>The passage of the Pūrvaśaila’s BP is regarded in the Tarkajvālā as proof that worship of bodhisattvas by monks is supported by buddhavacana, and the passage is summarized in Candrakīrti’s Triśaraṇasaptati verse 51. On the other hand, “worship of bodhisattvas” is introduced by the Chinese monk-pilgrim Yijing 義浄 as a marker that separates the Hīnayāna and Mayāhāna. It can be seen that Bhāviveka, Candrakīrti, and Yijing shared the same awareness of the problem. It is assumed that the Bodhisattva to be worshipped was probably a lay Bodhisattva.</p>