金光明最勝王經疏 4.572

4.572

贊曰：四成佛時，云同時。五所得果，謂無上菩提。六佛名號。問：無處無容同時同處有二如來，如何五十億同時得作佛？答：約化佛土說二不俱，亦約現相不得同時，據他用土及應合作則說同時。又或國劫名字雖同，據方器界各別，得同時作佛。

Commentary: Fourth, the time of attaining buddhahood: it says "at the same time." Fifth, the fruit attained, meaning unexcelled bodhi. Sixth, the name and title of the Buddha. Question: There is no place and no possibility for two Tathāgatas to exist at the same time and in the same place; how can five billion become buddhas at the same time? Answer: In terms of transformation lands (nirmāṇakṣetra), it is said that two do not coexist, and in terms of manifested marks they cannot be simultaneous; but based on lands of enjoyment for others (parasaṃbhogakṣetra) and when it is fitting to act together, simultaneity is spoken of. Furthermore, although the names of the realms and kalpas are identical, based on distinct directional physical realms (bhājanadhātu), they can become buddhas at the same time.