Devibhagavatapurana 11.21.23

Devībhāgavatapurāṇa 11.21.23

gāyatrīcchando mantrasya yathāsaṅkhyākṣarāṇi ca |
tāvallakṣāṇi kartavyaṃ puraścaraṇakaṃ tathā ||