大般涅槃經疏 1.21

1.21

復次五序序於三點，如是總序三點不縱不橫不並不別乃稱如是，我聞序般若，一時序解脫，住處序法身，同聞序三點不虛。

Furthermore, the five prefaces preface the three dots: 'Thus' generally prefaces the three dots being neither vertical nor horizontal, neither parallel nor distinct, and only then is called 'Thus'; 'I have heard' prefaces prajñā; 'at one time' prefaces liberation; 'dwelling place' prefaces the dharmakāya; and 'hearing together' prefaces the three dots not being empty.