Chazal tell us that the world exists because of the merit of the children
learning Torah with their Rebbe. From this we learn that the spiritual
reward for teaching children Torah is very great. The Shechina dwells
wherever children learn Torah with their Rebbe. Rebbe Shimeon Bar Yochai
once said, when going to visit a cheder, that he was going to see the face
of the Shechinah. (Zohar, Lech Lecha). And, indeed, it was the custom
of people who were dedicated to Torah to visit the cheder when they had
completed their work in order to see the face of the Shechinah. Anyone who
enters a cheder should be aware that he enters a place where the Shechinah
extends Her wings protectively over Her young. The Rebbe must keep this in
mind, apply himself faithfully to his sacred task and see to it that the
cheder is kept clean: “your camp should be holy.” Rebbes should be aware
that they are responsible for instilling faith in the young.
A Rebbe must prepare himself for class so that he can answer questions
correctly. The verse “cursed is he who does the work of G-d with deceit” (Yermiah
48:10) applies to a Rebbe who doesn’t prepare himself adequately and gives
his talmidim wrong information. Moreover, the time spent in teaching
misinformation is time wasted which can never be recovered, time in which
the Rebbe actually prevents the talmidim from learning Torah.
The verse “cursed is he who does the work of G-d with deceit” (Yermiah
48:10) also applies to a Rebbe who comes late to class or leaves the class
in the middle of the lesson: he is depriving his talmidim of the opportunity
to learn Torah. For this reason, the Rama (Shulchan Oruch Choshen Mishpat
ח"ס ו"ש) writes that a Rebbe should not stay up too late at night because it
may impair his ability to teach the next day. He should also avoid fasting,
even in atonement of averos he may have done, for this, too, may impair his
teaching. A Rebbe who was unable to daven before class should rather daven
by himself during the break than delay his class. Every minute of learning
is precious to G-d. For this reason, a person should avoid disrupting a
class to speak to the Rebbe or one of the talmidim unless it is about an
urgent matter that must be addressed before the break.
If any worker who is given an hourly wage is forbidden to be late or to
leave early, certainly a Rebbe, whose work is so important, must be careful
to avoid cutting his lessons short because he is late or leaves in the
middle of his class. According to the Zohar, the learning of the
children he teaches negates harmful decrees against the Jewish People.
Of course, if a Rebbe needs to pause to take a drink, etc. in order to keep
up his strength to teach, he is permitted to do so. He should have no
hesitations. Similarly, the break between classes and other things which the
children need in order to renew their ability to learn contribute to the
learning and are permitted.