摩訶止觀 1.57

1.57

若其心念念知三惡苦多、人間苦樂相間、天上純樂，為天上樂關六根不出、六塵不入，此上品善心、行於天道。

If in thought after thought one's mind knows that the three evil destinies are full of suffering, that the human realm has suffering and pleasure mixed, and that the heavens are pure bliss, and for the sake of heavenly pleasure one shuts the six sense faculties so they do not go out and the six sense objects so they do not enter, this is the superior grade of wholesome mind and traversing the heavenly path.