Śatapatha Brāhmaṇa ("of a hundred paths") 1.5.1.7

1.5.1.7

manuṣvadbharatavaditi | manurha vā agre yajñeneje tadanukṛtyemāḥ prajā yajante tasmādāha manuṣvaditi manoryajña ityu vā āhustasmādvevāha manuṣvaditi

'Like as Manu (did), like as Bharata;'--Manu, indeed, worshipped with sacrifice in olden times, and doing as he did these descendants of his now sacrifice: therefore he says 'like as Manu.' Or, say they, (it means) 'at the sacrifice of Manu,' and therefore he says 'as (he did) with Manu.'