成唯識論演祕 3.201

3.201

意辨論中根、身雙舉，根微細故不唯言根，身濫外塵不獨云身，故兼言之二失皆遣。

The intention is to explain why the Treatise mentions both "faculties" and "body": because the faculties are subtle, it does not only say "faculties"; because "body" could be confused with external dust, it does not say "body" alone. Therefore, by mentioning both, both faults are dispelled.