金剛三昧經論 3.57

3.57

論曰：真俗無二一實之法，諸佛所歸名如來藏。今此品中明無量法及一切行莫不歸入如來藏中，故就所入以立名也。

The commentary states: The one real dharma in which the ultimate and conventional are non-dual, that to which all buddhas return, is called the tathāgatagarbha. Now in this chapter, it explains that immeasurable dharmas and all practices without exception return and enter into the tathāgatagarbha; hence the title is established with respect to that which is entered.