Śatapatha Brāhmaṇa ("of a hundred paths") 9.1.2.26

9.1.2.26

atha jaghanārdhenodak | himasya tvā jarāyuṇāgne parivyayāmasi pāvako asmabhyaṃ śivo bhaveti yadvai śītasya praśītaṃ taddhimasya jarāyu śītasya tvā praśītena śamayāma ityetat

Then northwards along the hind part (of the altar), with (Vâg. S. XVII, 5), 'With an outer vesture of cold we encompass thee, O Agni: be thou bright and propitious unto us!'--that part of the cold which is frozen hard is an outer vesture of cold: thus, 'By the frozen part of cold we appease thee!'