Śatapatha Brāhmaṇa ("of a hundred paths") 1.6.3.16

1.6.3.16

tadveva khalu hato vṛtraḥ | sa yathā dṛtirniṣpīta evaṃ saṃlīnaḥ śiśye yathā nirdhūtasakturbhastraivaṃ saṃlīnaḥ śiśye tamindro 'bhyādudrāva haniṣyan

Now Vritra, on being struck, lay contracted like a leather bottle drained of its contents, like a skin bag with the barley-meal shaken out. Indra rushed at him, meaning to slay him.