Brahmavaivartapurana 3.57.102

Brahmavaivartapurāṇa 3.57.102

maṇiratnaṃ kaustubhaṃ ca yo nārāyaṇavakṣasi .
bhikṣāṃ kṛtvā tu dāsyāmi kṛtvā nārāyaṇavratam .. 99 ..