俱舍論疏 29.44

29.44

論「三淨解脫身作證具足住」，釋第三解脫。故《正理》云「彼瑜伽師久觀不淨，厭惡轉故令心沈慼。為欲策發令暫生歡，或為暫解久修勞倦，或為自審驗不淨觀堪能，故彼復依第四靜慮，於欲界色起淨勝解，先取寶衣、花等淨相，由勝解力漸廣思惟，遍於所緣作淨行相。如契經說：彼於後時應取少淨相總思惟諸色。此雖策心而不掉舉，雖觀淨相而不起貪。既知善根勢力增上，次復於境略聚其心，於一所緣觀淨而住，此位名曰淨解脫滿，能究竟捨不淨想故。此淨解脫，亦如第二內無色想觀外諸色（已上論文）。」

The treatise stating "Third: the pure liberation, having bodily realized it, one abides fully endowed" explains the third liberation. Therefore the Nyāyānusāra says: "Because that yogin has long contemplated impurity, their mind sinks into dejection due to the operation of revulsion. In order to stimulate it to temporarily arouse joy, or to temporarily relieve the fatigue of long cultivation, or to test for oneself the capability of the contemplation of impurity, that person further relies on the fourth dhyāna to arouse pure resolve regarding forms of the desire realm: first grasping pure marks such as precious garments and flowers, by the power of resolve gradually and broadly reflecting, universally producing pure aspects regarding the objective support. As the sūtra says: 'That person subsequently should grasp a few pure marks and comprehensively reflect upon forms.' Although this stimulates the mind, there is no restlessness; although one contemplates pure marks, greed does not arise. Knowing that the power of wholesome roots has increased, one next concentrates the mind briefly on the object, dwelling in contemplation of the pure regarding a single objective support—this stage is called the fulfillment of the pure liberation, because it can completely abandon the ideation of impurity. This pure liberation is also like the second: having no ideation of internal form, one contemplates external forms (above is the text of the treatise)."