Shatapatha Brahmana 5.1.1.10

5.1.1.10

tadu vai yajetaiva | ya evametaṃ yajñaṃ kLptaṃ vidyurṛkto yajuṣṭaḥ sāmato ye prajajñayasta enaṃ yājayeyureṣā ha tvetasya yajñasya samṛddhiryadenaṃ vidvāṃso yājayanti tasmādu yajetaiva

Let him none the less sacrifice: whatever (priests) thus know that sacrifice properly, in respect of the Rik, the Yagus, and the Sâman, and such as are proficient, let them assist him in offering it; for verily this is the perfection of that sacrifice, when wise (priests) assist him in offering it: let him therefore sacrifice by all means.