Śatapatha Brāhmaṇa ("of a hundred paths") 3.2.1.17

3.2.1.17

sa prorṇute | viṣṇoḥ śarmāsi śarma yajamānasyetyubhayaṃ vā eṣo 'tra bhavati yo dīkṣate viṣṇuśca yajamānaśca yadaha dīkṣate tadviṣṇurbhavati yadyajate tadyajamānastasmādāha viṣṇoḥ śarmāsi śarma yajamānasyeti

He covers himself, with the text, 'Thou art Vishnu's refuge, the refuge of the sacrificer.' He who is consecrated indeed becomes both Vishnu and a sacrificer; for when he is consecrated, he is Vishnu; and when he sacrifices, he is the sacrificer: therefore he says, 'Thou art Vishnu's refuge, the refuge of the sacrificer.'