The works of Ādi Śaṅkarācārya

Chāndogyopaniṣadbhāṣyam

Verse 390

अथ यत्सत्रायणमित्याचक्षते ब्रह्मचर्यमेव तद्ब्रह्मचर्येण ह्येव सत आत्मनस्त्राणं विन्दतेऽथ यन्मौनमित्याचक्षते ब्रह्मचर्यमेव तद्ब्रह्मचर्येण ह्येवात्मानमनुविद्य मनुते ॥ २ ॥

In plain words

Now, what people call the great sacrificial session is nothing other than celibacy, for through continence one secures the protection of the true Self. And what they call silence is also celibacy, for having realized the Self through continence, one truly comprehends.

Close to the Sanskrit

Now, what they call the sacrificial session—that is celibacy indeed, for through celibacy indeed one finds the protection of the true Self. And what they call silence—that is celibacy indeed, for having realized the Self through celibacy, one reflects.