無量壽經優婆提舍願生偈註 1.76

1.76

佛本何故起此莊嚴？見有如來，眷屬欲供養他方無量諸佛、或欲教化無量眾生，此沒彼出先南後北，不能以一念一時放光普照遍至十方世界教化眾生，有出沒前後相故。是故興願：願我佛土諸大菩薩，於一念時頃遍至十方作種種佛事。是故言無垢莊嚴光，一念及一時，普照諸佛會，利益諸群生。

Why did the Buddha originally raise this adornment? He saw that there are Tathāgatas whose retinues, wishing to make offerings to immeasurable Buddhas of other realms or wishing to teach and transform immeasurable sentient beings, disappear here and appear there, first in the south and then in the north, unable in a single thought-moment and at one time to emit light that universally illuminates, reaching everywhere throughout the worlds of the ten directions to teach and transform sentient beings, because they have the characteristics of emerging and disappearing, before and after. Therefore he made the vow: "I vow that all the great bodhisattvas in my Buddha land shall, in the span of a single thought-moment, reach everywhere throughout the ten directions to perform various Buddha activities." Therefore it is said: "Immaculate adorned light, / In a single thought-moment and at one time, / Universally illuminates the assemblies of all Buddhas / And benefits all living beings."