大方廣圓覺修多羅了義經略疏 1.295

1.295

以己最尊之頂，禮佛最卑之足，敬之至也。敬是意業，意業無狀，故以身、口表之。經標白言及下歎大悲，即口業矣。

Using one's own most venerable crown to bow to the Buddha's most base feet is the utmost of respect. Respect belongs to mental action; mental action having no visible form, it is expressed through body and speech. The sūtra's statement 'said to' and the praise of great compassion below are bodily and vocal action.