Śatapatha Brāhmaṇa ("of a hundred paths") 7.4.2.29

7.4.2.29

atha 'rtavye upadadhāti | ṛtava ete yadṛtavye ṛtūnevaitadupadadhāti madhuśca mādhavaśca vāsantikāvṛtū iti nāmanī enayorete nāmabhyāmevaine etadupadadhāti dve iṣṭake bhavato dvau hi māsāvṛtuḥ sakṛtsādayatyekaṃ tadṛtuṃ karoti

He then lays down two Ritavya (seasonal bricks);--the two seasonal (bricks) being the same as the seasons, it is the seasons he thus lays down. [Vâg. S. XIII, 25] 'Madhu and Mâdhava, the two spring seasons,'--these are the names of those two: it is thus by their names that he lays them down. There are two (such) bricks, for two months are a season. He 'settles' them once: he thereby makes (the two months) one season.