। । । । ॥ २१ ॥
In plain words
Once born and given a name and form, the body is consecrated by Mantras through Jātakarma and the other rites. Upanayana makes this same body a Brahmacārin; marriage makes it a Gṛhastha; the forest rite makes it a Tāpasa; and withdrawal from ritual action makes it a Parivrāṭ. These names and Saṃskāras belong to the body, with its particular Jāti and lineage. You are distinct from all of them.
Close to the Sanskrit
That body, once born and given a name and form, is consecrated by Mantras through Jātakarma and the other rites. Through the Saṃskāra of Upanayana it is then designated a Brahmacārin. Through the Saṃskāra of union with a wife that same body is designated a Gṛhastha. Through the Saṃskāra of forest dwelling it is designated a Tāpasa. Through the Saṃskāra marked by withdrawal from action it is designated a Parivrāṭ. Thus the body, with its own Jāti, lineage, and Saṃskāras, is different from you.