Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 33: Kuśanābha’s Daughters marry Brahmadatta
Text 1.33.13
सा च तं प्रणता भूत्वा शुश्रूषणपरायणा।
उवास काले धर्मिष्ठा तस्यास्तुष्टोऽभवद्गुरुः॥
sā ca taṁ praṇatā bhūtvā śuśrūṣaṇa-parāyaṇā
uvāsa kāle dharmiṣṭhā tasyās tuṣṭo ’bhavad guruḥ
sā ca = that lady; tam praṇatā bhūtvā = surrendering unto him; śuśrūṣaṇa-parāyaṇā = and having become absorbed in services to him; uvāsa = resided near him; kāle = in a short while; dharmiṣṭhā = fixed in vedic dharma; tasyāḥ = with her; tuṣṭaḥ = became satisfied; abhavat = became; guruḥ = the guru.
That lady fixed in Vedic dharma, surrendering unto him, and having become absorbed in services to him, resided near him. In a short while the guru became satisfied with her.
Because he was a Brahmaṛṣi, he is referred to as a guru here.