Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 18: The Advent of Rāma, Lakṣmaṇa, Bharata and Śatrughna
Text 1.18.40

तस्य चिन्तयमानस्य मन्त्रिमध्ये महात्मनः।
अभ्यागच्छन्महातेजा विश्वामित्रो महामुनिः॥

tasya cintayamānasya mantri-madhye mahātmanaḥ
abhyāgacchan
mahā-tejā viśvāmitro mahā-muniḥ

tasya = that; cintayamānasya = while was contemplating about it; mantri-madhye = in the midst of his ministers; mahā-ātmanaḥ = great soul Daśaratha; abhyāgacchat = arrived; mahā-tejāḥ = the great sage; viśvāmitraḥ = Viśvāmitra; mahā-muniḥ = of great prowess.

While that great soul Daśaratha was contemplating about it in the midst of his ministers, the great sage Viśvāmitra of great prowess arrived.

The author described the descent of the Supreme Personality of Godhead up till now. From now onwards, he will describe the purposes for which He had descended: protection of His saintly devotees, destruction of the miscreants and establishment of religious principles. His primary purpose is protection of His saintly devotees while His destruction of the miscreants is incidental, just as growing crops is the primary purpose of a farmer while removal of weeds that prevent crops from growing is incidental. In order to describe His protection of His saintly devotees while destroying the miscreants, the sage Vālmīki begins to describe the episode of Viśvāmitra. It should be understood that Lord Rāma will also establish dharma.

Viśvāmitra is described here as mahā-tejāḥ (“of great prowess”), indicating that though he was personally capable of executing the purpose for which he had arrived, he wanted to reveal Lord Rāma’s glory through his arrival.