瑜伽論記 4.257

4.257

淨解脫中，已得捨念圓滿清白者，此釋淨義。一剎那中，離過名清，相續離過名白。以此為依，修習清淨聖行圓滿名淨解脫者，此依第四定於青等四色隨觀一色作清淨解，亦可總觀四色作清淨解，如觀花樹。後勝處中，方別觀四色，此中說得捨念淨故。下復以三義釋此淨名云：謂已超過諸苦樂故亂動靜故，善磨瑩故，故淨解脫唯在第四根本非近分，此亦內無色而觀外色由前已說故此略之。

In the pure liberation, "having attained equanimity and mindfulness that are perfected, pure and bright" explains the meaning of "pure." In a single moment, being free of faults is called "pure"; in continuity, being free of faults is called "bright." Having this as a basis, cultivating pure noble practices to perfection is called "pure liberation": relying on the fourth dhyāna, with respect to the four colors such as blue, one contemplates any one color and forms a pure resolution; one may also collectively contemplate the four colors and form a pure resolution, like contemplating flowering trees. Only later, in the stations of mastery, are the four colors contemplated separately; here it is said because of attaining the purity of equanimity and mindfulness. Below, it further explains this name "pure" with three meanings, stating: "Because one has surpassed all suffering and pleasure, because of the agitation of motion and rest, and because of being well polished." Therefore, the pure liberation exists only in the fundamental state of the fourth [dhyāna], not in the preparatory stage. This is also internally without form while contemplating external forms; since this was explained previously, it is omitted here.