坐禪三昧經 2.8

2.8

已棄喜故，諦知憶念樂護，聖人言樂護，餘人難捨，樂中第一，過此以往，無復樂也。是故一切聖人，於一切淨地中，說慈為第一樂。樂則是患。所以者何？第一禪中心不動轉，以無事故，有動則有轉，有轉則有苦，是故三禪以樂為患。復以善妙捨此苦樂，先棄憂喜除苦樂意，護念清淨得入第四禪。不苦不樂護清淨念一心，是故佛言：「護最清淨第一，名第四禪。」以第三禪樂動故，名之為苦，是故四禪除滅苦樂，名不動處。

Having abandoned joy, he carefully understands, remembers, and guards bliss with equanimity. The noble ones speak of the equanimity of bliss; for others it is difficult to relinquish, the foremost among pleasures, beyond which there is no further bliss. Therefore all noble ones, among all pure planes, speak of loving-kindness as the foremost bliss. Bliss is itself an affliction. Why? In the foremost dhyāna the mind does not stir or turn because there are no affairs; where there is stirring there is turning, and where there is turning there is suffering; therefore the third dhyāna considers bliss to be an affliction. Furthermore, with subtle excellence he relinquishes this suffering and bliss; having previously cast aside sorrow and joy, he removes the mind of suffering and bliss, and with purity of equanimity and mindfulness attains entry into the fourth dhyāna. Neither suffering nor pleasant, with equanimity, pure mindfulness, and one-pointedness of mind; therefore the Buddha said: 'Equanimity is the most pure and foremost; it is called the fourth dhyāna.' Because the bliss of the third dhyāna moves, it is called suffering; therefore the fourth dhyāna eliminates suffering and bliss, and is called the unmoving place.