Śatapatha Brāhmaṇa ("of a hundred paths") 2.3.3.20

2.3.3.20

sapta caiva śatāni viṃśatiśca | saṃvatsare saṃvatsare ha vā asyāgnihotram mahatokthena sampadyate saṃvatsare saṃvatsare mahadukthamāpnoti ya evaṃ vidvānagnihotram juhotyetadu hāsyāgnihotram mahatokthena sampadyate mahadukthamāpnoti

Seven hundred and twenty. Thus, indeed, his Agnihotra is accomplished, year after year, with the great chant; and year after year does he obtain the great chant, whosoever, knowing this, offers the Agnihotra.