瑜伽論記 12.115

12.115

由是菩薩此住無間下，第四明安立染污不染污，謂第八地無功用故一向清淨，七地有功用故名雜，此第七地初得無相是第八地前導故名不染，未得根本無相尚有功用有所希求未能任運無相故墮雜染。

From "Due to this, the bodhisattva immediately after this dwelling..." downwards, the fourth [section] explains establishing the defiled and undefiled: because the eighth stage is effortless, it is purely clean; because the seventh stage involves effort, it is called mixed. This seventh stage first attains marklessness and is the vanguard of the eighth stage, hence it is called undefiled; yet, not having attained the fundamental marklessness, it still involves effort and has something sought, unable to function marklessly spontaneously, and thus falls into defilement.