Śatapatha Brāhmaṇa ("of a hundred paths") 8.7.1.2

8.7.1.2

yadveva 'rtavyā upadadhāti | kṣatra vā ṛtavyā viśa imā itarā iṣṭakāḥ kṣatraṃ tadviśyattāraṃ dadhāti tāḥ sarvāsu citiṣūpadadhāti sarvasyāṃ tadviśi kṣatramattāraṃ dadhāti

And, again, as to why he lays down seasonal (bricks),--the seasonal (ones) are the nobility and these other bricks are the peasantry: he thus places the nobility as the eater among the peasantry. He lays down (some of) them in all the layers: he thus places the nobility as the eater among the whole people.