תּוֹרָה קנג

The student and the teacher are the aspect of sun and moon. And if the student has a face [panim] — that is, is in the aspect of luminous face [anpin n'hirim] — then he can receive the light of the teacher's face — until the light of the teacher's face is actually visible in his face.

Like the moon that receives the sun's light. And this is the matter of greeting the face of a Torah scholar — that is, receiving the teacher's face within one's own face literally.

But if the student has no face — that is, he is in the aspect of dark face [anpin chashuchin] because he is submerged in the desire for money — then the teacher's face is not seen within him. And likewise one who is brazen-faced also has no holy face — and cannot receive the teacher's face within his face as above.