法華義疏 3.119

3.119

《大品》不明二乘作佛，但明菩薩作佛，其義易解，如用藥為藥，故不名祕密。《法華》明二乘作佛，望昔為難解，如用毒作藥，故稱祕密。

The Pañcaviṃśatisāhasrikā Prajñāpāramitā Sūtra does not clarify that the two vehicles attain Buddhahood, but only clarifies that bodhisattvas attain Buddhahood; its meaning is easy to understand, like using medicine as medicine, and so it is not called esoteric. The Lotus Sūtra clarifies that the two vehicles attain Buddhahood, which in comparison to the past is difficult to understand, like using poison as medicine; therefore it is called esoteric.