Rāmāyaṇacampū 1.98

1.98

There, having cursed Rambhā, who had been sent by the enemy of Jambha, saying, ‘Become a rock!’, while he was performing austerities in the eastern quarter with breath suppressed, the Lotus-seated One, whose friend the sun was distressed by the heat of the fire of his austerities, appeared and said: ‘Because you have conquered your senses, you are a brahmarṣi; let Vasiṣṭha also address you thus.’
He obtained the status of a brahmarṣi by the direction of Vasiṣṭha,
just as a twice-born achieves Vedic luster from the sacrament of investiture. (98)