Shatapatha Brahmana 3.7.1.31

3.7.1.31

so 'dhvaryuḥ | yūpaśakalamevājuhottadahaiṣa svagākṛta āsīttatho rakṣāṃsi yajñaṃ nānūdapibantāyaṃ vai vajra udyata iti

The Adhvaryu, then, offered up only a chip of the stake, and thereby that (sacrificer) was bid good-speed; and thus the Rakshas did not thereafter sip the sacrifice, thinking, 'that surely is a raised thunderbolt.'