यो वाचि तिष्ठन् वाचोऽन्तरो यं वाङ्न वेद यस्य वाक्शरीरं यो वाचमन्तरो यमयत्येष त आत्मान्तर्याम्यमृतः ॥३,७.१७ ॥
In plain words
He who dwells in speech, yet is within speech, whom speech does not know, whose body speech is, who from within controls speech — he is thy Self, the inner controller, the immortal.