James 3:1 - Coke's Commentary on the Holy Bible

Be not many masters— Many teachers. The word Διδασκαλος among the Jews, commonly signified the same with Rabbi, a title of which the Scribes and Pharisees were exceedingly fond, as it signifies frequently the head of a sect, or author of a doctrine, Matthew 23:7. But in that sense no Christians are to desire the title, much less to assume the thing thereby intended; for Christ alone is our Master, or the author of the doctrines which we are to embrace. But the word is here used in a more general sense, and the verse may be thus paraphrased: "Give me leave, my brethren, to caution you against another evil, which I have seen some reason to apprehend; and to press you, that you be not many teachers; that none of you rashly undertake the office of teachers, into which many are ready to intrude themselves, without due qualifications, or a real divine call: but I would urge you to be cautious against such an assuming disposition, as knowing that we who bear that office, must expect that we shall undergo greater and stricter judgment than others in a more private station of life."