觀無量壽佛經義疏 2.51

2.51

"'First, filial support of parents and serving teachers and elders, having a mind of compassion without killing, and cultivating the ten virtuous actions.'" Since this is the cause for Buddhahood in the three times, we clearly know it is the great practice of bodhisattvas. The first is shared with the actions of ordinary beings; the second is shared with the actions of the two vehicles; the third is the unshared action of the Great Vehicle. Therein are four phrases. The upper two phrases are the practice of repaying kindness: the kindness of parents in giving birth and raising, and the kindness of teachers and elders in guiding and teaching. The lower two phrases are the practice of abandoning evil. Non-killing is the foremost of the ten virtues, hence it is specifically singled out: the body eliminates the three evils, the mouth abandons the four faults, and the mind cuts off the three unwholesome actions.