Śatapatha Brāhmaṇa ("of a hundred paths") 1.3.5.7

1.3.5.7

tāḥ pañcadaśa sāmidhenyaḥ saṃpadyante pañcadaśo vai vajro vīryaṃ vajro vīryamevaitatsāmidhenīrabhisaṃpādayati tasmādetāsvanūcyamānāsu yaṃ dviṣyāttamanguṣṭhābhyāmavabādhetedamahamamumavabādha iti tadenametena vajreṇāvabādhate

Fifteen sâmidhenî verses result (from this repetition of the first and last of the eleven verses). The fifteen-versed chant, doubtless, is the thunderbolt, and the thunderbolt means strength; so that he thereby converts the sâmidhenîs into strength: hence, if he should hate any one, he may crush him with his great toes at the time when those (verses) are recited. By saying, 'I here crush so and so!' he crushes him with that thunderbolt.