BṚHADĀRAṆYAKA UPANISHAD · 3.7.17

यो वाचि तिष्ठन् वाचो ऽन्तरो यं वाङ् न वेद यस्य वाक् शरीरं यो वाचम् अन्तरो यमयत्य् एष त आत्मान्तर्याम्य् अमृतः ॥

yo vāci tiṣṭhan vāco ’ntaro yaṃ vāṅ na veda yasya vāk śarīraṃ yo vācam antaro yamayaty eṣa ta ātmāntaryāmy amṛtaḥ ॥

'He who dwells in the tongue (vâk), and within the tongue, whom the tongue does not know, whose body the tongue is, and who pulls (rules) the tongue within, he is thy Self, the puller (ruler) within, the immortal.'

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)