Śatapatha Brāhmaṇa ("of a hundred paths") 6.7.3.16

6.7.3.16

tribhirupatiṣṭhate | traya ime lokā atho trivṛdagniryāvānagniryāvatyasya mātrā tāvataivāsmā etannihnute 'tho tāvataivainametadebhyo lokebhyaḥ śamayati

With three (verses) he stands by worshipping;--three in number are these worlds, and threefold is Agni: as great as Agni is, as great as is his measure, with so much he thereby makes amends to him, and with so much does he thereby appease him towards these worlds.