Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 65: Viśvāmitra Becomes a Brahmarṣi
Text 1.65.4

स कृत्वा निश्चयं राम तप आतिष्ठदव्ययम्॥

sa kṛtvā niścayaṁ rāma tapa ātiṣṭhad avyayam

saḥ = he; kṛtvā = resolved [to conquer anger]; niścayam = firmly; rāma = O Rāma; tapaḥ = austerities; ātiṣṭhat = executed; avyayam = and undeteriorating.

O Rāma, he firmly resolved [to conquer anger] and executed undeteriorating austerities.