Torah 230 · תורה ר״ל

Know! someone who has eyes to see, can see and recognize in the disciple’s face who his teacher is, provided he has at one time seen the teacher. This is because “A person’s wisdom enlightens his face” (Ecclesiastes 8:1). Thus it is that when the student receives his teacher’s wisdom, he receives [the features of] his face.

This is why a person should look at his teacher’s face when receiving his wisdom, as it is written, “Your eyes shall behold your teacher” (Isaiah 30:20). For the wisdom is in the face, as explained above. Therefore, as explained above, when someone looks at the student’s face, he is able to know who his teacher is.