Became A teacher by the age of 16 Capable enough to teach without textual reference

This person could be the best teacher for all the students this teacher doesn't need any kind of textual reference to teach any student

This teacher could be the best teacher I've seen in my whole student life
This person doesn't need any kind of textual reference to teach

He taught me whole commerce syllabus before one month of exam and I passed it when I had lost all my hope of passing it. He is just an angel for students.