金光明經文句記 6.173

6.173

初、「善哉」下二行，就果佛讚所游定。諸根寂滅者，以了眼等性常、具無減修，諸惑死生悉已寂滅，故常居寂定。而復游入者，將軫法輪，表不妄說。又三世佛說必須入定，故《首楞嚴經》云「雖知諸法常是定相，而示眾生諸禪差別。」言善寂大城者，正讚所入定也。即向經初法性三昧，若入此定即能善了諸法寂滅，無非法性故。防生死之非、禦涅槃之敵，即中道善寂而名大城也。亦名無垢清淨三昧等，既是佛之境界，故受無垢清淨之名。為諸佛行處也。

First, the two lines from "Excellent!" downward praise the samādhi traversed in terms of the fruit Buddha. "All sense faculties are quenched and extinguished": because he has comprehended that the nature of the eyes and the rest is eternal and complete without need for supplementary cultivation, and all afflictions and births and deaths are completely quenched and extinguished, he constantly abides in quiescent samādhi. Yet he traverses and enters it again because he is about to turn the wheel of Dharma, symbolizing that he does not speak falsely. Furthermore, when the Buddhas of the three periods speak, they must enter samādhi; hence the Śūraṅgama Sūtra says: "Although knowing that all dharmas are constantly the mark of samādhi, they show sentient beings the distinctions of the various dhyānas." Calling it the "great city of excellent quiescence" directly praises the entered samādhi. That is, it is the Dharmatā Samādhi mentioned at the beginning of the sūtra; if one enters this samādhi, one can skillfully comprehend that all dharmas are quenched and extinguished, because none are not dharmatā. Guarding against the faults of birth and death and defending against the adversary of nirvāṇa, it is precisely the excellent quiescence of the Middle Way that is named the "great city." It is also called the "stainless, pure samādhi" and the like; since it is the realm of the Buddha, it receives the name "stainless and pure." It is the domain traversed by all Buddhas.