若如来随彼所欲而方便说，即是大乘，无有三乘。三乘者入于一乘，一乘者即第一义乘。
《胜鬘师子吼一乘大方便方广经》
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If the Tathagata, in accordance to individual disposition, teaches through skillful means, then it is the Mahayana and not the Three Vehicles. The Three Vehicles are included in the One Vehicle, and the One Vehicle is the Vehicle of Ultimate Truth.
The Lion’s Roar of Queen Srimala, the Single-Vehicle Great Expedience, the Corrective and Extensive Sutra [Srimaladevi Simhanada Sutra]
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第一义乘是圆满的、是具足三乘道的；二乘法却不能触及第一义，所修、所证、所说、所学都不能及于第一义。因为二乘法只是方便道，只能让人出离分段生死，不能触及法界实相，何况能究竟法界的实相。
《胜鬘经讲记》第三辑，页308
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The Vehicle of Ultimate Truth is perfect and completely covers the Three-Vehicle paths. However, the Two Vehicles cannot touch upon the Ultimate Truth; what are so practiced, realized, taught, and learned also cannot touch upon the Ultimate Truth. The reason is that the Two Vehicles are just expedient ways, which only help people transcend the delimited existence. However, they are unable to touch upon the reality of the dharma-realm, not to mention being unable to thoroughly and completely realize the reality of the dharma-realm.
A Discourse on the Srimaladevi Simhanada Sutra,
Vol. 3, p.308