Śatapatha Brāhmaṇa ("of a hundred paths") 3.1.1.8

3.1.1.8

tāṃ vā etām pariśrayanti | nedabhivarṣāditi nveva varṣā devānvā eṣa upāvartate yo dīkṣate sa devatānāmeko bhavati tira iva vai devā manuṣyebhyastira ivaitadyatpariśritaṃ tasmātpariśrayanti

They enclose it on every side, lest it should rain upon (the sacrificer, while being consecrated): this, at least, is (the reason for doing so in) the rainy season. He who is consecrated, truly draws nigh to the gods, and becomes one of the deities. Now the gods are secreted from men, and secret also is what is enclosed on every side: this is why they enclose it on every side.