法華論疏 2.443

2.443

令眾生知得清淨故者，釋開佛知見意也。所以開佛知見者，令眾生知故也。得清淨者，令眾生知佛得清淨。又一意：令眾生知，使眾生得清淨。

"Causing sentient beings to know and attain purity" explains the meaning of "opening the Buddha's knowledge and vision." The reason for opening the Buddha's knowledge and vision is to cause sentient beings to know [it]. "Attain purity" means causing sentient beings to know that the Buddha has attained purity. Another interpretation: causing sentient beings to know, so as to enable sentient beings to attain purity.