首楞嚴義疏注經 8.192

8.192

同佛地，如來藏也，即前地如佛地，本來具足無漏性德。此德能為萬行所依，故云清淨因。依於此因能起趣果之行，故云依因發揮取涅槃道。道即因也，此則萬德為萬行因，萬行為涅槃因。合理之行，行從理起，故云隨順平等。能生妙果，名曰善根。

"Ground identical to the Buddhas" refers to the tathāgatagarbha; this is the preceding "ground like the ground of the Buddhas," which inherently possesses the uncontaminated virtues of nature. Because these virtues can serve as the foundation for the myriad practices, it is called the "pure cause." Because based on this cause one can give rise to practices that tend toward the fruit, it says: "relying on the cause, they give expression to it and grasp the path to nirvāṇa." "Path" is indeed the cause; thus the myriad virtues are the cause for the myriad practices, and the myriad practices are the cause for nirvāṇa. Practice that accords with principle, practice arising from principle, is therefore called "accordance with the equal." Being able to engender the wondrous fruit, it is named "wholesome roots."