Śatapatha Brāhmaṇa ("of a hundred paths") 13.1.2.9

13.1.2.9

tadāhuḥ yatprājāpatyo'śvo'tha kathāpyanyābhyo devatābhyaḥ prokṣatīti sarvā vai devatā aśvamedhe'nvāyattā yadāha sarvebhyastvā devebhyaḥ prokṣāmīti sarvā evāsmindevatā anvāyātayati tasmādaśvamedhe sarvā devatā anvāyattāḥ pāpmā vā etam bhrātṛvya īpsati yo'śvamedhena yajeta vajro'śvaḥ paro martaḥ paraḥ śveti śvānaṃ caturakṣaṃ hatvādhaspadamaśvasyopaplāvayati vajreṇaivainamavakrāmati nainam pāpmā bhrātṛvya āpnoti

Concerning this they say, 'Seeing that the horse is sacred to Pragâpati, wherefore (does he say), "I sprinkle thee" for other deities also?' Well, all the gods are concerned in the horse-sacrifice; when he says, 'I sprinkle thee for all the gods,' he makes all the gods take a concern in the horse-sacrifice; whence all the gods are concerned in the horse-sacrifice. But his wicked enemy seeks to lay hold of him who performs the horse-sacrifice, and the horse is a thunderbolt;--having killed the four-eyed dog, he--with 'Undone is the man! undone is the dog!'--plunges it under the horse's feet: it is by means of the thunderbolt he thus stamps him down; and the wicked enemy does not lay hold of him.