Śatapatha Brāhmaṇa ("of a hundred paths") 3.3.4.15

3.3.4.15

śyeno bhūtvā parāpateti | vaya evainametadbhūtam prapātayati yadvā ugraṃ tannāṣṭrā rakṣāṃsi nānvavayantyetadvai vayasāmojiṣṭham baliṣṭhaṃ yacyenastamevaitadbhūtam prapātayati yadāha śyeno bhūtvā parāpateti

'Having become a falcon, fly away!' he thereby makes him fly forward after becoming a falcon; for the evil spirits fly not after what is fearful: now he, the falcon, forsooth is the most fearful, the strongest of birds, and as such a one he makes him (Soma) fly forwards when he says, 'Having become a falcon, fly away!'