{Be not many teachers} (m(8820)polloi didaskaloi ginesthe).
Prohibition with m(885c) and present middle imperative of ginomai.
"Stop becoming many teachers" (so many of you). There is thus a
clear complaint that too many of the Jewish Christians were
attempting to teach what they did not clearly comprehend. There
was a call for wise teachers (verses  13f. ), not for foolish
ones. This soon became an acute question, as one can see in I
Cor. 12 to 14. They were not all teachers ( 1Co 12:28f.  14:26 ).
The teacher is here treated as the wise man ( 3:13-18 ) as he
ought to be. The rabbi was the teacher ( Mt 23:7f.  Joh 1:38  3:10  20:16 ). Teachers occupied an honourable position among the
Christians ( Eph 4:11  Ac 13:1 ). James counts himself a teacher
(we shall receive,  3:1 ) and this discussion is linked on with
 1:19-27 . Teachers are necessary, but incompetent and unworthy
ones do much harm. {Heavier judgment} (meizon krima). "Greater
sentence." See  Mr 12:40  Lu 20:47  for perrisoteron krima (the
sentence from the judge,  Ro 13:2 ). The reason is obvious. The
pretence of knowledge adds to the teacher's responsibility and
condemnation.