इदं वाव तज्ज्येष्ठाय पुत्राय पिता ब्रह्म प्रब्रूयात्प्रणाय्याय वान्तेवासिने ॥ ३.११.५ ॥
In plain words
A father may tell this Brahman to his eldest son, or to a worthy pupil,
The commentators
Chāndogyopaniṣadbhāṣyam· bhāṣya
इदं वाव तद्यथोक्तम् अन्योऽपि ज्येष्ठाय पुत्राय सर्वप्रियार्हाय ब्रह्म प्रब्रूयात् । प्रणाय्याय वा योग्याय अन्तेवासिने शिष्याय ॥
In plain words
As stated, any qualified teacher may impart this Brahman to his eldest son who is dear to him in every way, or to a devoted and capable resident disciple.
Close to the Sanskrit
This indeed as stated, another also should impart Brahman to the eldest son, who is deserving of all affection; or to a devoted, competent resident pupil, the disciple.