Śatapatha Brāhmaṇa ("of a hundred paths") 6.8.1.3

6.8.1.3

taddhaika āhuḥ | svayaṃ vā eṣa vanīvāhito viṣṇukramairvā eṣa prayāti vātsapreṇāvasyatīti na tathā vidyāddaivaṃ vā asya tatprayāṇaṃ yadviṣṇukramā daivamavasānaṃ yadvātsapramathāsyedam mānuṣam prayāṇaṃ yadidam prayāti mānuṣamavasānaṃ yadavasyati

Here now some say, 'It is by himself that he (Agni) is driven about; for by the Vishnu-strides he drives forward, and by the Vâtsapra he unyokes.' Let him not think this to be so; for divine (to the gods) is that progress of his, to wit, the Vishnu-strides; and divine the unyoking, to wit, the Vâtsapra. But human would be that progress of his, which he makes in this manner, and human the unyoking he makes.