大乘起信論義記 1.110

1.110

三、但依經文不能解意，因他廣論得解經意，故云無自心力也。此有文持無義持故。

Third, merely relying on sūtra texts they cannot understand the intent, but depending on another's extensive śāstra they can understand the sūtras' intent; hence it says "lack power in their own minds." This is because they have the retention of text but lack the retention of meaning.