大乘起信論義記 3.17

3.17

「雖有」下，釋緣起甚深義，即染而不染也。《勝鬘經》云「自性清淨心難可了知，彼心為煩惱所染亦難了知。」乃至結云唯佛能知。《楞伽經》中亦同此說，故彼經云「如來藏是清淨相，客塵煩惱垢染不淨。」乃至廣說。下結云「我今與汝及諸菩薩甚深智者，能了別也。」

From "Although there is" downward, explaining the extremely profound meaning of pratītyasamutpāda, which is being undefiled while defiled. The Śrīmālādevīsiṃhanādasūtra says: "The intrinsically pure mind is difficult to comprehend; that that mind is defiled by afflictions is also difficult to comprehend"; up to concluding that only the Buddha can know it. The Laṅkāvatārasūtra also speaks in the same way, as that sūtra says: "The tathāgatagarbha has the characteristic of purity, yet it is defiled and impure by adventitious defilements"; and so forth at length. Below it concludes: "Now I, together with you and those bodhisattvas of profound wisdom, are able to comprehend it."