Agnipurana 33.8

33.8

prārthya tanmaṇḍalāyādau gāyatryā bandhayennaraḥ /
oṃ nārāyaṇāya vidmahe vāsudevāya dhīmahi //

Having prayed thus to the maṇḍala at first, a man should tie it with the Gāyatrī: / "Om, we know Nārāyaṇa; we meditate on Vāsudeva;