瑜伽論記 13.31

13.31

由此建立是佛世尊下，第二答答中，隨問即為三答。此即答初問也。謂賴耶微細，地前菩薩隨教生解未能了達，故於二乘不為分別，故云密記所以不說。

From 'Established through this, the Buddha, the World-Honoured One...' below, in the second part, the answer, three answers are given corresponding to the questions. This is the answer to the first question. That is, the ālaya is subtle, and bodhisattvas before the stages generate understanding according to teaching without having fully penetrated it; therefore, for the two vehicles it is not distinguished for them; hence it says it was kept a secret teaching, which is why it was not spoken of.