Vaishnava Dharmashastra 90.20

90.20

māghyāṃ samatītāyāṃ kṛṣṇadvādaśyāṃ sopavāsaḥ śravaṇaṃ prāpya śrīvāsudevāgrato mahāvartidvayena dīpadvayaṃ dadyāt ||

(If) on the twelfth day of the (the dark half following on the full moon day of the month Mâgha, moon enters Sravana), he must keep a fast till the moon has entered that asterism, and place two lamps with two large wicks near (an image of) Vâsudeva;