Shatapatha Brahmana 4.5.8.1

4.5.8.1

tadyatraitattrirātre sahasraṃ dadāti | tadeṣā sāhasrī kriyate sa prathame 'haṃstrīṇi ca śatāni nayati trayastriṃśatam caivameva dvitīye 'haṃstrīṇi caiva śatāni nayati trayastriṃśataṃ caivameva tṛtīye 'haṃstrīṇi caiva śatāni nayati trayastriṃśataṃ cāthaiṣā sāhasryatiricyate

Now when at that Trirâtra sacrifice he gives those thousand (cows), then that one is made the one-thousandth. On the first day he brings three hundred and thirty-three; and likewise on the second day he brings three hundred and thirty-three; and likewise on the third day he brings three hundred and thirty-three. Then that one-thousandth is left over.