俱舍論記 29.34

29.34

「論曰至為第八解脫」者，釋初句。一於內色身有色想貪。為除想貪，觀外不淨青瘀等色，而方內身令貪不起，名初解脫。二於內色身無色想貪。雖已除貪，為堅牢故，觀於外不淨青瘀等色令貪不起，名第二解脫。三觀淨色，令貪不起，名淨解脫，顯觀轉勝。此淨解脫，彼觀行者身中證得，名身作證。具足圓滿得住此定，名具足住。空無邊等四無色定，各能解脫下地貪故，為次四解脫。滅受想定，棄背受等，名第八解脫。故《婆沙》八十四云「棄背義是解脫義。問：若棄背故名解脫者，何等解脫棄背何心？答：初、二解脫棄背色貪心，第三解脫棄背不淨觀心，四無色處解脫各自棄背次下地心，想受滅解脫棄背一切所緣心。故棄背義是解脫義（廣如《婆沙》）。」

Regarding "the treatise says, up to: is the eighth liberation": this explains the first line. First, there is the ideation of and attachment to form regarding the internal physical body. In order to remove this ideation and attachment, one contemplates external impure forms such as lividity and the like, and matching it to the internal body, prevents attachment from arising; this is called the first liberation. Second, regarding the internal physical body there is no ideation of or attachment to form. Although attachment has already been removed, in order to make [this detachment] firm, one contemplates external impure forms such as lividity and the like to prevent attachment from arising; this is called the second liberation. Third, one contemplates pure forms and prevents attachment from arising; this is called the pure liberation, showing that the contemplation has become superior. This pure liberation is directly realized within the body of that practitioner of contemplation, which is termed "realizing it with the body." Possessing it fully and being able to abide in this concentration is termed "fully abiding." The four immaterial concentrations, such as the infinity of space and the like, because they each can liberate one from attachment to the stage below, constitute the next four liberations. The concentration of the cessation of ideation and feeling, abandoning and turning away from feeling and ideation, is called the eighth liberation. Thus fascicle 84 of the Mahāvibhāṣā says: "The meaning of abandoning and turning away is the meaning of liberation. Question: If it is called liberation because of abandoning and turning away, which liberation abandons and turns away from which mind? Answer: The first and second liberations abandon and turn away from the mind of attachment to form; the third liberation abandons and turns away from the mind of the contemplation of impurity; the liberations of the four immaterial bases each abandon and turn away from the mind of the next lower stage; the liberation of the cessation of ideation and feeling abandons and turns away from all minds with cognitive objects. Therefore, the meaning of abandoning and turning away is the meaning of liberation." (As explained in detail in the Mahāvibhāṣā).