Shatapatha Brahmana · Chapter 14.8.1

śāṃtibrāhmaṇam
ॐpūrṇamadaḥ pūrṇamidaṃ pūrṇātpūrṇamudacyate/ pūrṇasya pūrṇamādāya pūrṇamevāvaśiṣyata ॐ khaṃ brahma khaṃ purāṇaṃ vāyuraṃ khamiti ha smāha kauravyāyaṇīputro vedo'yaṃ brāhmaṇā vidurvedainena yadveditavyam - १४.८.१