瑜伽師地論略纂 8.195

8.195

論解時中云「此淨色相於現在世雖有淨相，於未來世不當不淨，如今現在外不淨色，無有是處」者，此中意，明今時淨色，於未來世必當不淨。其既觀外有不淨境，觀內身云若未來世即為淨，內身若不當不淨，如今現在外不淨一種，無有是處，必當不淨，不云當不淨也。

Where the treatise explains time, saying, “Although these clean colors and marks have a clean appearance in the present life, that they will not be foul in a future life—just as external foul colors in the present—is impossible”: the intention here clarifies that clean colors of the present time will definitely become foul in a future life. Having already contemplated external foul objects, one contemplates the internal body, saying that if in a future life it were to be clean, and if the internal body were not to become foul just as the single kind of external foulness in the present, this is impossible; it will definitely become foul, not that it will fail to become foul.