Shatapatha Brahmana 10.3.4.4

10.3.4.4

sa ha vai yattaduvāca vettha catvāri mahānti vettha catvāri mahatām mahāntītyagnirmahāṃstasya mahato mahadoṣadhayaśca vanaspatayaśca taddhyasyānnaṃ vāyurmahāṃstasya mahato mahadāpastaddhyasyānnamādityo mahāṃstasya mahato mahaccandramāstaddhyasyānnam puruṣo mahāṃstasya mahato mahatpaśavastaddhyasyānnametānyeva catvāri mahāntyetāni catvāri mahatām mahāntyetānyeva catvāri vratānyetāni catvāri vratānāṃ vratānyetānyeva catvāri kyānyetāni catvāri kyānāṃ kyānyeta eva catvāro'rkā ete catvāro'rkāṇāmarkāḥ

Now, when he said, 'Knowest thou the four great (things)? Knowest thou the four great of the great?'--the great one is Agni (the fire), and the great (thing) of that great one are the plants and trees, for they are his food; and the great one is Vâyu (the wind), and the great (thing) of that great one are the waters, for they are his (the wind's) food; and the great one is Âditya (the sun), and the great (thing) of that great one is the moon, for that is his food; and the great one is Man, and the great (thing) of that great one is cattle, for they are his food:--these are the four great things, these the four great of the great;--these are the four rites, these the four rites of rites;--these are the four relating to Ka, these the four deepest relating to Ka;--these are the four flames, these the four flames of flames.