Śatapatha Brāhmaṇa ("of a hundred paths") 3.4.2.8

3.4.2.8

te devāḥ | juṣṭāstanūḥ priyāṇi dhāmāni sārdhaṃ samavadadire te hocuretena naḥ sa nānāsadetena viṣvaṅyo na etadatikrāmāditi taddevā apyetarhi nātikrāmanti ke hi syuryadatikrāmeyuranṛtaṃ hi vadeyurekaṃ ha vai devā vrataṃ caranti satyameva tasmādeṣāṃ jitamanapajayyaṃ tasmādyaśa evaṃ ha vā asya jitamanapajayyamevaṃ yaśo bhavati ya evaṃ vidvāntsatyaṃ vadati tadetattānūnaptraṃ nidānena

The gods laid down together their favourite forms and desirable powers, and said, 'Thereby he shall be away from us, he shall be scattered to the winds, whosoever shall transgress this (covenant) of ours!' And even now the gods do not transgress that (covenant), for how would they fare, were they to transgress it?--they would speak untruth, and verily there is one law which the gods do keep, namely, the truth. It is through this that their conquest, their glory is unassailable: and so, forsooth, is his conquest, his glory unassailable whosoever, knowing this, speaks the truth. Now, the Tânûnaptra is really that same (covenant of the gods).