法華義疏 7.175

7.175

夫前教未得開後教，後教必得開前，龍樹但當教明義，故作此說。又實有斯義，所以作此釋之。後教開前者，命小人而說大法有二種義：一者、得密教小人，二者、得顯教菩薩。若命菩薩而說大法，則唯得顯教菩薩，不得密教二乘也。

Prior teachings cannot reveal subsequent teachings, but subsequent teachings must reveal prior ones; Nāgārjuna was only explaining the meaning according to that teaching, and so he made this statement. Furthermore, this meaning truly exists, which is why he gave this explanation. The subsequent teaching revealing the prior means that commanding lesser people to preach the great Dharma has two meanings: first, one succeeds in esoterically teaching lesser people; second, one succeeds in explicitly teaching bodhisattvas. If he had commanded bodhisattvas to preach the great Dharma, he would only have succeeded in explicitly teaching bodhisattvas, and would not have succeeded in esoterically teaching the two vehicles.