This paper examined, the reasons the Sarvāstivāda School regards anuśaya ― which is considered a synonym for kleśa, as an important concept of the Sarvāstivādin Path. From the Sangītiparyāya and the Dharmaskandha, the Sarvāstivāda School classifies the kleśa explained by Āgamas and the Nikāyas into (1) saṃyojana, (2) bandhana, (3) anuśaya, (4) upakleśa, and (5) paryavasthāna. These develop into Abhidharmakośabhāṣya chapter 2 on Indriya as contaminated caitasika among the "five categories." Since the citta and caitasika share (1) āśraya, (2) ālambana, (3) ākāra, (4) kāla, and (5) dravya, which means pañcasamatā, the contaminated caitasika adversely affects the citta. Abhidharmakośabhāṣya chapter 2 focuses on the corresponding relationship between the citta and caitasika.
Chapter 5 on anuśaya mainly covers anuśaya-related matters. From Prakaraṇapāda, the Sarvāstivāda School interprets anuśaya, as (1) aṇu, (2) anuśerate, (3) anugata, and (4) anubadhanti, explaining the characteristics and the principles of the operation of anuśaya that are difficult to abandon even with a religious practice. Among the four, the most crucial concept is anuśerate, which reinforces its strength by contaminating according to ālambanatas and saṃprayogatas. According to Sarvāstivāda School, kleśa is maintained and grown in sāsrva-dharma.
For the Sarvāstivāda School, the abandonment of anuśaya is not the destruction of anuśaya itself but is freeing from the bondage of the acquiring anuśaya, which means the acquisition of nirvana (visaṃyoga-prāpti). In addition, each stage of visaṃyoga is described as a parijña. In the Abhidharmakośabhāṣya, parijña is classified into jñāna- parijña and prahāṇa-parijña, and nine parijña are set on the prahāṇa-parijña. This presents an epistemological aspect such as yathābhūtajñanadarśana and the practical aspects of jñāna and prahāṇa, indicating that the insights into sāsrva-dharma, leads to the severing of bondage of anuśaya.