Śatapatha Brāhmaṇa ("of a hundred paths") 5.3.1.4

5.3.1.4

atha śvo bhūte | mahiṣyai gṛhānparetya ādityaṃ caruṃ nirvapatīyaṃ vai pṛthivyaditiḥ seyaṃ devānām patnyeṣā vā etasya patnī bhavati tasmādādityo bhavatyetadvā asyaikaṃ ratnaṃ yanmahiṣī tasyā evaitena sūyate tāṃ svāmanapakramiṇīṃ kurute tasyai dhenurdakṣiṇā dhenuriva vā iyam manuṣyebhyaḥ sarvānkāmānduhe mātā dhenurmāteva vā iyam manuṣyānbibharti tasmāddhenurdakṣiṇā

And on the following day, he goes to the dwelling of the Queen, and prepares a pap for Aditi; for Aditi is this Earth, and she is the wife of the gods; and that (queen) is the wife of that (king): hence it is for Aditi. And she, the Queen, assuredly is one of his (the king's) jewels: it is for her that he is thereby consecrated, and he makes her his own faithful (wife). The sacrificial fee, on her part, is a milch cow; for this (earth) is, as it were, a milch cow: she yields to men all their desires; and the milch cow is a mother, and this (earth) is, as it were, a mother: she bears (or sustains) men. Hence the fee is a milch cow.