Zeal is a virtue that makes us procure the glory of God with great affection.

A zealous teacher instructs his students, in the first place, by his good example. This is the first lesson he gives, thus imitating Jesus Christ, who began by doing before teaching. In fact, he may wish to attain the proposed end, but he will do so only by the longest path if he is content merely with speaking; the shortest path is that of example. Children learn more by seeing than by hearing. "The most striking and effective discourse," says Saint Bernard in his Second Sermon on the Life of Saint Benedict, "is the example of good works. Nothing better persuades others of what we say than the example that shows how easy it is to practice the counsels we offer." A teacher is like a lamp placed on a lamp stand, which, of course, gives light by its shining but which must also warm by its heat. Thus he procures the glory of God with great affection when he labors in a truly effective manner at his own sanctification.

Next, he instructs by solid teaching. This is the second kind of instruction he gives his students, and a most important one it is, because he teaches them things they are ignorant of and that they need to know so that they may know, love, and serve God. This function is most honorable, no doubt, but as we have already said, how many trials, fatigues, labors, and disappointments must he endure to fulfill it properly! Thus the teacher procures the glory of God with great affection when he labors generously and without any material interest in view of the salvation of his neighbor by leading him to the practice of what is right.

Finally, he teaches by wise and moderate corrections; such is the third lesson that he gives, and it, too, is essential. How many faults that need to be corrected are there not in a child—an evil leaven, a defective germ that the teacher must eliminate; but that he will not exterminate except insofar as he admonishes the students without ceasing, remonstrating with them at the proper times, and also punishing them when necessary but always in a gentle and charitable way. Thus he will procure the glory of God with great affection when he labors for the salvation of his neighbor by employing an unfailing diligence, assiduous attention, and unshakable courage to bring them to flee evil.

In a teacher, Zeal is thus a most excellent virtue, and it is for this reason, says Saint John Chrysostom, that he who chastises his body by austerities has less merit than he who wins souls for God. Saint Gregory adds that there is no sacrifice more agreeable to God than Zeal (On Ezechiel, homily two).

Characteristically, this virtue is active: this is its distinctive mark. With what eagerness and what exactness does not a good teacher, for instance, fulfill the duties of his state if he has real Zeal?

First, his religious obligations—his first duty is to achieve perfection. In order to maintain himself in piety, to preserve the spirit of his calling, and not to succumb to dissipation of mind or the drying up of his heart (the common result of profane studies), he will look upon as more necessary than ever the religious practices ordained by his Constitutions, especially daily meditation, spiritual reading, examination of conscience, the fervent reception of the sacraments, annual retreats, and so forth. In general, he will strive not to fail against any point of regularity. He will make it a point to arrive before the spiritual exercise begins, rather than afterward. Whether the thing he has to do is more or less important, easy or difficult, it suffices that obedience should require it or recommend it, and he will be ready; he will hasten wherever the Rule calls him; he will be pleased to be there and will remain there as long as duty demands it.

Secondly, his responsibility for educating the students—the education of youth demands, on the part of those who are charged therewith, the most assiduous attention, the most constant effort, and concern for the most minute details. How can a teacher bear the weight of a ministry that might daunt the boldest courage unless he is filled with great Zeal for the salvation of his students? He should, therefore, experience something of the tender and restless affection of Saint Paul, who felt with regard to the Galatians "in the pain of childbirth until Christ is formed in you" (4:19). Thus he will draw all his satisfaction, all his joy, from teaching all the children without any shirking, any distinctions, any preferences, even though they may be ignorant, inept, meagerly endowed by nature, rich or poor, well- or ill-disposed, Catholic or Protestant, and so forth.

Ardently desiring the salvation of his students, he will labor for this as much as he possibly can by his good works, prayers, and Communions. In a word, he will with all his heart seek to save all of them without exception, being convinced that there is no soul that has not cost the blood of Jesus Christ; and he will teach them what they need to do so as to profit by this admirable redemption.

But genuine Zeal is not only active; it is also enlightened and prudent. A teacher truly zealous for the instruction of his students makes himself all things to all people, following the example of the Apostle (1 Corinthians 9:22), becoming little with the little ones, that is, conforming himself to their level of understanding and manner of appreciating things; he will take into consideration their weakness, their limited degree of intelligence and reason, while using more elevated language with those who are capable of understanding it. In all this he acts so as to instruct the students to their greatest advantage.

Nor should he limit himself to formal instruction, following the rules of discourse with order and method. He will cleverly make use of the occasions that always happen to bring in, as though by chance, some moral maxims that, not being expected, are all the better welcomed and ordinarily make more of an impression than carefully constructed lessons against which the students are sometimes on guard.

Finally, Zeal must be charitable and courageous; thus it makes the teacher act with strength and Gentleness—with strength because it is magnanimous and incapable of getting discouraged when encountering pains and difficulties; with Gentleness because it is mild, tender, compassionate, and humble—in a word, conformable to the Spirit of Jesus Christ.

A teacher lacks Zeal:
1) When he is indifferent and does not do all he can to spread the kingdom of God in all the ways we have indicated, especially by giving nothing but good example to the children; they naturally imitate what they see their guides do and, unfortunately, the wrong more easily than the right; they remember the example of a single defect rather than that of many virtues;
2) When he has no genuine desire to work for the salvation of his students and neglects to procure for them the means of achieving this goal as far as his profession obliges him to do, and
3) When he is not active in trying to instruct them well and lacks ardor in applying himself to his own perfection.

There is, however, a false zeal that can easily be recognized:
1) When passion is its principle;
2) When it is set in motion by an annoyance offered, an affront, an act of hatred, a disappointment, or an antipathy;
3) When it is the effect of nothing but ill-humor, inclination, aversion, self-love;
4) When in teaching we seek to have one class rather than another or to remain in a city where our vanity, laziness, and love of ease more readily find satisfaction;
5) When we prefer certain students to others because they are more agreeable to deal with;
6) When we seek to publicize our success or the pains we take to make the students improve;
7) When we love applause and praise;
8) When we are peeved because others succeed better than ourselves;
9) When we threaten or reprove using injurious terms, cutting language, bitter or angry words, or words lacking in discretion, without considering that imprudent zeal often does more harm than discreet zeal does good;
10) When we show ourselves to be restless, biting, bitter, and excitable;
11) When we give in to complaining, murmuring, sadness, discouragement, and malignant interpretations;
12) When we seek temporal benefits rather than the glory of God and our neighbor’s spiritual advancement;
13) When we show ourselves without indulgence or mercy, without patience, humility, or charity;
14) When in extraordinary or unusual circumstances we fail to take advice from those who are there to guide and direct us.

I will most gladly spend and be spent for you (2 Corinthians 12:15).
Woe to me if I do not proclaim the Gospel (1 Corinthians 9:16).
Let love inflame your zeal, wisdom inform it, and perseverance make it permanent; so that it be at once ardent, circumspect, and undefeated with nothing lukewarm in it, yet discreet, though never cowardly. (Saint Bernard, On the Song of Songs, Sermon 20, London: Mowbray, 1952, p. 51)