首楞嚴義疏注經 1.426

1.426

袒，肉袒也，致敬之極。西方俗儀，見王者必肉袒示，非敢有犯。佛教亦隨此用，然此以表將荷大法之重擔耳。

Baring means baring the flesh, the utmost expression of respect. In the secular etiquette of the Western regions, upon seeing a king one must bare the flesh to show that one does not dare commit any transgression. Buddhism also follows this usage; however, here it represents the intention to shoulder the heavy burden of the Great Dharma.