Verse 4.9.2

ब्रह्मविदिव वै सोम्य भासि को नु त्वानुशशासेत्यन्ये मनुष्येभ्य इति ह प्रतिजज्ञे भगवांस्त्वेव मे कामे ब्रूयात् ॥ ४.९.२ ॥

brahmavidiva vai somya bhāsi ko nu tvānuśaśāsetyanye manuṣyebhya iti ha pratijajñe bhagavāṃstveva me kāme brūyāt || 4.9.2 ||

2. The teacher said: ‘Somya, you shine like one who has known Brahman. Who taught you?’ Satyakāma assured him: ‘Certainly no human being. But will you, O Lord, please teach me now about Brahman, the subject closest to my heart?’.

Word-for-word explanation:

Brahmavit iva vai somya bhāsi, [the teacher, Gautama, said to Satyakāma,] Somya, you are shining like one who has known Brahman; kaḥ nu tvā anuśaśāsa iti, who taught you; anye manuṣyebhyaḥ, somebody other than a human being; iti ha pratijajñe, he assured him; bhagavān tu eva me kāme bruyāt, but, Lord, teach me now about Brahman, the subject closest to my heart.

Commentary:

The look on Satyakāma’s face surprised his teacher. He looked like a knower of Brahman. He was shining.

What are the signs of a person who has known Brahman? According to Śaṅkara, that person is happy and cheerful, with a smile on his face all the time. His mind is always under control, as are his sense organs. He is also free from desires and therefore from worries.

Satyakāma had these signs. This is why his teacher asked him who had taught him. Satyakāma emphatically said that no human being had taught him. He meant thereby that so long as his teacher was there he needed no other human being to teach him. He also assured his teacher that he had now come to him to learn about Brahman, the subject dearest to him.