大乘起信論義記 1.85

1.85

第二者，與下分別發趣道相而作因緣。以彼文中令利根者發決定心，進趣大道，堪任不退住位故。此當十信終心，自分滿足，故云善根成熟。進入十住正定聚中，使前信心堪任不退故也。

The second serves as the condition for the below [passage on] "Differentiating the Characteristics of Setting Forth toward the Path." This is because that text causes those of sharp faculties to generate a resolute mind, advance toward the Great Path, and be capable of the stage of non-retrogression (the abodes). This corresponds to the final mind of the ten faiths, where one's own portion is fulfilled; hence it says "wholesome roots have matured." Entering into the correct determination of the ten abodes enables the preceding faithful mind to become capable of non-retrogression.