'तस्माद्ब्रह्मैवाचार्यरूपेणावतिष्ठते' इति व्यासस्मृतेः ।
In plain words
'So it is Brahman itself, and nothing less, that takes its stand before you in the form of the teacher' — that is Vyāsa's smṛti, and it is on that authority the point rests.
Close to the Sanskrit
'Therefore Brahman itself abides in the form of the teacher' — thus, from the smṛti of Vyāsa.