釋氏要覽 2.15

2.15

The Baihu tong states: Why do people bow to one another? It is to express sentiments and show intention, bending their status and humbling their bodies to revere their superiors. "Bowing" [bai] means submission. In secular custom, two bows model yin and yang. Now, the Buddhists take three prostrations as primary, representing the devotion and reverence of the three karmas. The [Dazhi]du lun states: The internal protocol of prostration generally pertains to the karma of body and speech. The Buddha-Dharma takes mind as root and body and speech as branches; therefore, three prostrations serve as the measure of etiquette.