तस्मै स विद्वानुपसन्नाय सम्यक् प्रशान्तचित्ताय शमान्विताय ।येनाक्षरं पुरुषं वेद सत्यं प्रोवाच तां तत्त्वतो ब्रह्मविद्याम् ॥ १३ ॥
In plain words
To the one who had approached properly, whose Citta was fully calm and who was endowed with śama, that knowing one declared according to tattva the Brahmavidyā by which one knows the true Akṣara Puruṣa.
The commentators
Muṇḍakopaniṣadbhāṣyam· bhāṣya
तस्मै स' विद्वान् गुरुर्ब्रह्मवित्, उपसन्नाय उपगताय । सम्यक् यथाशास्त्रमित्येतत् । प्रशान्तचित्ताय उपरतदर्पा दिदोषाय । शमान्विताय बाह्येन्द्रियोपरमेण च युक्ताय, सर्वतो विरक्तायेत्येतत् । येन विज्ञानेन यया विद्यया च परया अक्षरम् अदृश्यादिविशेषण तदेवाक्षर पुरुषशब्द- वाच्य पूर्णत्वात्पुरि शयनाच्च, सत्य तदेव परमार्थस्वाभा- व्यादव्ययम्, अक्षर चाक्षरणादक्षतत्वादक्षयत्वाच्च, वेद विजा- नाति ता ब्रह्मविद्या तत्त्वत यथावत् प्रोवाच प्रब्रूयादित्यर्थ । आचार्यस्याप्ययमेव नियमो यन्न्यायप्राप्तसच्छिष्यनिस्तार- णमविद्यामहोदधे ॥
In plain words
The “knowing one” is the guru who knows Brahman, and the teaching is given to the student who has truly approached. “Properly” means as the śāstra directs. A student whose Citta is at peace has let faults such as pride subside; one endowed with śama has quieted the outer senses and become dispassionate toward every object. Through higher vidyā, the student knows the Akṣara described as invisible and by the other marks already given. This Akṣara is called Puruṣa because it is fullness itself and because it rests in the city of the body. It is satya, for ultimate reality is its very nature; it is imperishable and is called Akṣara because it never runs out, suffers no injury, and never decays. To say that the teacher “taught Brahmavidyā in accordance with truth, as it truly is” is to say that this is how the teacher must teach. An Ācārya has this obligation: when a worthy student comes in the prescribed way, to carry that student across the great ocean of avidyā.
Close to the Sanskrit
“That knower” is the guru who knows Brahman; “to him who has approached” means to the student who has come. “Properly” means in accordance with śāstra. “Whose Citta is completely at peace” means one from whom faults such as pride have ceased. “Endowed with śama” means also equipped with the withdrawal of the outer indriyas and dispassionate toward everything. By the realization that is higher vidyā one knows the Akṣara qualified as invisible and so on. That same Akṣara is denoted by the word Puruṣa because it is full and because it lies in the city. It alone is satya, imperishable because its nature is ultimate reality; it is called Akṣara because it does not flow away, is unimpaired, and does not perish. “He taught that Brahmavidyā in accordance with truth, as it truly is” means that he should teach it. This is also the rule for an Ācārya: to rescue from the great ocean of avidyā a worthy student who has come in the proper way.