大乘起信論裂網疏 6.60

6.60

不種善根，則此三昧名字不可得聞，況能修習。能修習此，當知是人必有善根。但善根深厚，則彼魔事無由得發。如日輪當空，必無魑魅。由善根微少乃致魔亂，所以前文勗令修行五悔也。

If one has not planted roots of goodness, then even the mere name of this samādhi cannot be heard, let alone being able to cultivate it. To be able to cultivate this, one should know that this person must possess roots of goodness. However, if their roots of goodness were deep and thick, those demonic events would have no way to arise. It is like the sun disk high in the sky: there will certainly be no mountain sprites or ghosts. It is because roots of goodness are slight and few that demonic disruption is brought on; this is why the previous text exhorted one to cultivate the five repentances.