維摩經玄疏 2.90

2.90

二、明修觀心者，若修此觀，還用前二觀雙忘、雙照之方便也。雙忘方便者，初觀知俗非俗，即是俗空；次觀知真非真，即是真空；忘俗非俗，忘真非真，非真非俗，即是中道。因是二空觀，入中道第一義諦。雖觀中道而不見者，皆是無明之所障也。當觀實相，修三三昧。《大智度論》云：「聲聞經中說『三三昧』，緣四諦十六行。摩訶衍明『三三昧』，但緣諸法實相。」

Second, explaining the cultivation of the contemplative mind: if one cultivates this contemplation, one again uses the expedients of twofold forgetting and twofold illuminating from the preceding two contemplations. As for the expedient of twofold forgetting, the initial contemplation knows that the conventional is not conventional, which is the emptiness of the conventional; the next contemplation knows that the ultimate is not ultimate, which is true emptiness. Forgetting that the conventional is not conventional, and forgetting that the ultimate is not ultimate, being neither ultimate nor conventional, is precisely the middle way. Relying on these two contemplations of emptiness, one enters the paramārtha-satya of the middle way. Although one contemplates the middle way, that one does not see it is entirely due to being obstructed by ignorance. One should contemplate the true mark and cultivate the three samādhis. The Mahāprajñāpāramitopadeśa states: 'In the śrāvaka sūtras, the "three samādhis" are explained as taking the four truths and the sixteen aspects as their conditions. The Mahāyāna clarifies that the "three samādhis" take only the true mark of all phenomena as their condition.'