瑜伽師地論略纂 10.50

10.50

論別解三因緣中，第三、田清淨云「當知略說能正發起如是加行，及正安住此加行果，名田清淨」者，謂無間、常委所作，發此加行時，及得隨地等攝前加行所希之果，乃至以佛為前前所希之果。此加行等若因果，皆堪能福田，故名田清淨。

Where the treatise individually explains the three causes and conditions, regarding the third, purity of the field, it says: "One should know that, briefly stated, being able to properly generate such application and properly abide in the fruit of this application is called the purity of the field." This means what is done without interruption and with continuous reverence; when initiating this application, and when obtaining the desired fruits subsumed under the preceding application according to the bhūmis and so forth, up to taking the Buddha as the desired fruit of the preceding ones. These applications and so forth, whether causes or fruits, are fully capable of serving as fields of merit; therefore it is called purity of the field.