大乘起信論略述 1.124

1.124

論。如是無漏至真如性相　述曰。此法合也。始本二覺名為無漏。本末不覺名曰無明。此二皆有業用顯現。故名為業。而非實有故名為幻。雖則如是。染淨不同。皆以真如而為體性。以動真如作此生滅。染淨二法無別體故。

The treatise says: "Just so, untainted [...] nature and aspect of tathatā."

The commentary says: This is the application to phenomena. The two awakenings, initial and original, are called "untainted"; fundamental and branch non-awakening are called "avidyā." Both of these have karmic functions that become apparent, and are thus called "karma"; yet they are not truly existent, and are thus called "illusion." Although this is so, and defilement and purity are distinct, they both have tathatā as their essence. Because tathatā is stirred to produce this arising and ceasing, the two phenomena of defilement and purity have no separate essence.