Śatapatha Brāhmaṇa ("of a hundred paths") 2.4.1.6

2.4.1.6

atha pra vā vrajati pra vā dhāvayati | sa yatra velām manyate tatsyanttvā vācaṃ visṛjate 'tha proṣya parekṣya yatra velām manyate tadvācaṃ yacati sa yadyapi rājāntareṇa syānnaiva tamupeyāt

Thereupon he walks or drives off; and having got as far as what he considers to be the boundary, he breaks silence. And when he returns from his journey he maintains silence from the moment he sees what he considers to be the boundary. And even though there be a king inside (one's house), one must not go to him (or any other person before one has rendered homage to the fires).