James 3:1

James is not trying to limit the number of teachers but rather to warn them against the dangers of false doctrines.

James indicates that judgment which was pronounced long ago [in Psalm 50:16-17].

Above the apostle spoke and taught that the faithful should have not faith alone, but together with good works. Now he passes to another equally significant commandment. Some undertake to teach what they themselves have not practiced. Such teachers, he says, receive no benefit, but …

Shall receive greater condemnation - For more offenses. St. James here, as in several of the following verses, by a common figure of speech, includes himself: we shall receive, - we offend, - we put bits, - we curse - None of which, as common sense shows, are to be interpreted either of him or of the other apostles.

Our judging others will but make our own judgment the more strict and severe, Matt. vii. Those who are curious to spy out the faults of others, and arrogant in passing censures upon them, may expect that God will be as extreme in marking what they say and do amiss. Another reason given against such acting the master is because we are all sinners: In many things we offend all,

My brethren, be not many masters,....

My brethren, be not many masters - “Be not many of you teachers.” The evil referred to is that where many desired to be teachers, though but few could be qualified for the office, and though, in fact, comparatively few were required. A small number, well qualified, would better discharge the duties of the office, and do more good, than many would; and there would be great evil in having many crowding themselves unqualified into the office.

The idea that faith (so called) without works (Jas 2:14-26) was all that is required, prompted "many" to set up as "teachers," as has been the case in all ages of the Church.

Be not many masters - Do not affect the teacher’s office, for many wish to be teachers who have more need to learn. There were many teachers or rabbins among the Jews, each affecting to have The truth, and to draw disciples after him. We find a caution against such persons, and of the same nature with that of St. James, in Pirkey Aboth, c. i. 10: Love labor, and hate the rabbin’s office. This caution is still necessary; there are multitudes, whom God has never called, and never can call, because he has never qualified them for the work, who earnestly wish to get into the priest’s office. And of this kind, in opposition to St. James, we have many masters - persons who undertake to show us the way of salvation, who know nothing of that ways and are unsaved themselves. These are found among all descriptions of Christians, and have been the means of bringing the ministerial office into contempt. Their case is awful; they shall receive greater condemnation than common sinners; they have not only sinned in thrusting themselves into that office to which God has never called them, but through their insufficiency the flocks over whom they have assumed the mastery perish for lack of knowledge, and their blood will God require at the watchman’s hand. A man may have this mastery according to the law of the land, and yet not have it according to the Gospel; another may affect to have it according to the Gospel, because he dissents from the religion of the state, and not have it according to Christ. Blockheads are common, and knaves and hypocrites may be found everywhere.