無量壽經優婆提舍願生偈註 2.107

2.107

何者為四？一者於一佛土身不動搖，而遍十方種種應化如實修行常作佛事。偈言「安樂國清淨，常轉無垢輪，化佛菩薩日，如須彌住持」故。開諸眾生淤泥華故。

[The Upadeśa says:] “What are the four? First, in a single buddha-land their bodies do not move, yet they pervade the ten directions with various responsive transformations, practicing in accordance with reality and constantly performing the Buddha's work. Because the verse says: ‘The Land of Peace and Bliss is pure; / the unstained wheel is constantly turned. / The transformed buddhas and bodhisattvas, like the sun, / sustain like Mount Sumeru,’ / in order to unfold the mud-dwelling blossoms of all living beings.”