Śatapatha Brāhmaṇa ("of a hundred paths") 7.3.2.12

7.3.2.12

tam pratyañcaṃ yantam | etāṃ citimavaghrāpayatyasau vā āditya eṣo 'śva imā u sarvāḥ prajā yā imā iṣṭakāstadyadavaghrādayatyasāveva tadāditya imāḥ prajā abhijighrati tasmādu haitatsarvo 'smīti manyate prajāpatervīryeṇa tadyatpratyañcaṃ yantamavaghrāpayati pratyaṅ hyevaiṣa yannimāḥ sarvāḥ prajā abhijighrati

Whilst it goes westward he makes it smell (kiss) that layer (of bricks);--that horse is yonder sun, and those bricks are the same as all these creatures (on earth): thus even as he makes (the horse) smell, so yon sun kisses these creatures. And hence, by Pragâpati's power, every one now thinks, 'I am!' And as to why he makes it smell while going westward, it is because, whilst going (from east) to west, that (sun) kisses all these creatures.