Śatapatha Brāhmaṇa ("of a hundred paths") 3.7.1.18

3.7.1.18

atha caṣālamudīkṣate | tadviṣṇoḥ paramam padaṃ sadā paśyanti sūrayaḥ divīva cakṣurātatamiti vajraṃ vā eṣa prāhārṣīdyo yūpamudaśiśriyattā viṣṇorvijitim paśyatetyevaitadāha yadāha tadviṣṇoḥ paramam padaṃ sadā paśyanti sūrayaḥ divīva cakṣurātatamiti

He then looks up at the top-ring with (Vâg. S. VI, 5; Rig-veda I, 22, 20), 'The wise ever behold that highest step of Vishnu, fixed like an eye in the heaven.' For he who has set up the sacrificial stake has hurled the thunderbolt: 'See ye that conquest of Vishnu!' he means to say when he says, 'The wise ever behold that highest step of Vishnu, fixed like an eye in the heaven.'