Valmiki Ramayana 7.13.21
अहं तु हिमवत्पृष्ठं गतो धर्ममुपासितुम् ।रौद्रं व्रत्तं समास्थाय नियतो नियतेन्द्रियः॥
ahaṃ tu himavatpṛṣṭhaṃ gato dharmamupāsitum |raudraṃ vrattaṃ samāsthāya niyato niyatendriyaḥ ||
Our plain-language meaning of this verse is waiting for scholar review.
Open in the book