Śatapatha Brāhmaṇa ("of a hundred paths") 4.6.9.17

4.6.9.17

sarparājñyā ṛkṣu stuvate | iyaṃ vai pṛthivī sarparājñī tadanayaivaitatsarvamāpnuvanti svayamprastutamanupagītaṃ yathā nānya upaśṛṇuyādati ha recayedyadanyaḥ prastuyādatirecayedyadanya upagāyedatirecayedyadanya upaśṛṇuyāttasmātsvayamprastutamanupagītam

They chant verses of the queen of serpents; for the queen of serpents is this earth: through her they thus obtain everything. The prelude is performed by (the Udgâtri) himself, and the chant is not joined in (by the choristers), lest some one else overhear it. For he would cause (the performance) to be in excess were another to chant; he would cause an excess, were another to join in it; he would cause an excess, were another to overhear it: therefore the prelude is performed by (the Udgâtri) himself, and the chant is not joined in.