成唯識論演祕 4.568

4.568

若也不許細障行爾。即應三地法觀恒行，以無有漏而為隔故。或不然者，顯彼細障有不行時即法觀起，前解為勝。

If one did not grant that the subtle obstacle functions thus, the contemplation of phenomena should be constantly active across the three [pure] bhūmis, because there is no sāsrava [mind] to separate it. Or 'were it not so' shows that when that subtle obstacle is inactive, the contemplation of phenomena arises; the prior explanation is superior.