Śāṅkhāyana (Kauṣītaki) Āraṇyaka 2.8

2.8

ŚĀ 2,8
mahāṁ indro ya ojasetyetayā gāyatrīm aśītiṃ pratipadyate stomair vatsasya vāvṛdha iti mahadvatyā vṛdhavatyā | mahadvad vṛdhavat | mahadvat - mahadvad dhyetad ahaḥ ||

ŚĀ 2.8
With 'Great is Indra, who by his might...' he begins the Gāyatrī eighty [triplets], and with 'With the stomata of Vatsa he grew...', which contains mahat and contains vṛdh. They contain mahat and contain vṛdh; for this day has the character of mahat, of mahat.