金剛三昧經論 2.172

2.172

經曰　大力菩薩言：「何謂存三守一入如來禪？」佛言：「存三者，存三解脫。守一者，守一心如。入如來禪者，理觀心如，入如是地即入實際。」

The sūtra says: Mahābalavān Bodhisattva said, "What is meant by preserving the three, guarding the one, and entering the tathāgata-dhyāna?" The Buddha said, "Preserving the three means preserving the three liberations. Guarding the one means guarding the one mind's thusness. Entering the tathāgata-dhyāna means that in contemplation of principle the mind is thus; entering such a stage is precisely entering the reality-limit."