大乘起信論義記 3.311

3.311

如是信心下，結位。初入正定聚不退者，顯於下無失也，謂入十住初發心住位，不墮凡小之地也。言名住如來種中正因相應者，明於上有得也，謂住習種性位，行順內熏之因，故云正因。又此位已去，定當得果，故云正因，以不更退失故。

From “faith in this way” onward concludes the rank. First, “enter the assembly of the definitively fixed, are non-retrogressing” shows that there is no falling away below; that is, entering the rank of the abode of initial generation of the mind among the ten abodes, one does not fall into the station of ordinary beings and the small [vehicle]. As for “are called those who abide in the lineage of the Tathāgatas, conjoined with the correct cause,” this clarifies that they have attained [virtue] above; that is, abiding in the rank of the nature of habit-practicing, their practice conforms to the cause of internal perfuming, hence it is called the “correct cause.” Furthermore, from this rank onward, they are certain to attain the fruition, hence it is called the “correct cause,” because they will no longer retrogress or fall away.