Shatapatha Brahmana 11.1.6.3

11.1.6.3

sa saṃvatsare vyājihīrṣat sa bhūriti vyāharatseyam pṛthivyabhavadbhuva iti taditamantarikṣamabhavatsvariti sāsau dyaurabhavattasmādu saṃvatsara eva kumāro vyājihīrṣati saṃvatsare hi prajāpatirvyāharat

At the end of a year he tried to speak. He said 'bhûh': this (word) became this earth;--'bhuvah': this became this air;--'svah': this became yonder sky. Therefore a child tries to speak at the end of a year, for at the end of a year Pragâpati tried to speak.