The Sages understood tsara’at, the theme of this week’s parsha, not as an illness but as a miraculous public exposure of the sin of lashon hara, speaking badly about people. Judaism is a sustained meditation on the power of words to heal or harm, mend or destroy. Just as God created the world with words, so we create and can destroy, relationships with words.

The rabbis said much about lashon hara, but virtually nothing about the corollary, Lashon tov, “good speech”. The phrase does not appear in either the Babylonian Talmud or the Talmud Yerushalmi. It figures only in two Midrashic passages where it refers to praising God. But lashon hara does not mean speaking badly about God.

It means speaking badly about human beings. If it is a sin to speak badly about people, is it a mitzvah to speak well about them? My argument will be that it is, and to show this, let us take a journey through the sources.

In Mishnah Avot, Ethics of the Fathers (2:10-11), we read the following:

Rabban Yochanan ben Zakkai had five (pre-eminent) disciples, namely Rabbi Eliezer ben Hyrcanus, Rabbi Joshua ben Chananya, Rabbi Yose the Priest, Rabbi Shimon ben Netanel, and Rabbi Elazar ben Arakh.

He used to recount their praise: Eliezer ben Hyrcanus: a plastered well that never loses a drop. Joshua ben Chananya: happy the one who gave him birth. Yose the Priest: a pious man. Shimon ben Netanel: a man who fears sin. Elazar ben Arakh: an ever-flowing spring.

However, the practice of Rabban Yochanan in praising his disciples seems to stand in contradiction to a Talmudic principle:

Rav Dimi, brother of Rav Safra said: Let no one ever talk in praise of his neighbour, for praise will lead to criticism. (Arakhin 16a)

Rashi gives two explanations for this statement. Having delivered excessive praise [yoter midai], the speaker himself will come to qualify his remarks, admitting for the sake of balance that the person of whom he speaks also has faults. Alternatively, others will point out his faults. For Rashi, the crucial consideration is, is the praise judicious, accurate, true, or it is overstated? If the former, it is permitted; if the latter, it is forbidden. Evidently, Rabban Yochanan was careful not to exaggerate.

Rambam, however, sees matters differently. He writes: “Whoever speaks well about his neighbour in the presence of his enemies is guilty of a secondary form of evil speech [avak lashon hara], since he will provoke them to speak badly about him” (Hilkhot Deot 7:4). According to the Rambam, the issue is not whether the praise is moderate or excessive, but the context in which it is delivered.

If it is done in the presence of friends of the person about whom you are speaking, it is permitted. It is forbidden only when you are among his enemies and detractors. Praise then becomes a provocation, with bad consequences.

Are these merely two opinions or is there something deeper at stake? There is a famous passage in the Talmud which discusses how one should sing the praises of a bride at her wedding:

Our Rabbis taught: How should you dance before the bride [i.e. what should one sing]?

The disciples of Hillel hold that at a wedding you should sing that the bride is beautiful, whether she is or not. Shammai’s disciples disagree. Whatever the occasion, don’t tell a lie. “Do you call that a lie?” the Hillelites respond. “In the eyes of the groom at least, the bride is beautiful.”

What’s really at stake here is not just temperament – puritanical Shammaites versus good-natured Hillelites – but two views about the nature of language. The Shammaites think of language as a way of making statements, which are either true or false. The Hillelites understand that language is about more than making statements. We can use language to encourage, empathiSe, motivate and inspire.

Or we can use it to discourage, disparage, criticise and depress. Language does more than convey information. It conveys emotion. It creates or disrupts a mood. The sensitive use of speech involves social and emotional intelligence. Language, in J. L. Austin’s famous account, can be performative as well as informative.

The argument between Hillel and Shammai is similar to that between Rambam and Rashi. For Rashi, as for Shammai, the key question about praise is: is it true, or is it excessive? For Rambam as for Hillel, the question is: what is the context? Is it being said among enemies or friends? Will it create warmth and esteem or envy and resentment?

We can go one further, for the disagreement between Rashi and Rambam about praise may be related to a more fundamental disagreement about the nature of the command, “You shall love your neighbour as yourself” (Lev. 19:18). Rashi interprets the command to mean: do not do to your neighbour what you would not wish him to do to you (Rashi to Sanhedrin 84b). Rambam, however, says that the command includes the duty “to speak in his praise” (Hilkhot Deot 6:3). Rashi evidently sees praise of one’s neighbour as optional, while Rambam sees it as falling within the command of love.

We can now answer a question we should have asked at the outset about the Mishnah in Avot that speaks of Yochanan ben Zakkai’s disciples. Avot is about ethics, not about history or biography. Why then does it tell us that Rabban Yochanan had disciples? That, surely, is a fact not a value, a piece of information not a guide to how to live.

However, we can now see that the Mishnah is telling us something profound indeed. The very first statement in Avot includes the principle: “Raise up many disciples.” But how do you create disciples? How do you inspire people to become what they could become, to reach the full measure of their potential? Answer: By acting as did Rabban Yochanan ben Zakkai when he praised his students, showing them their specific strengths.

He did not flatter them. He guided them to see their distinctive talents. Eliezer ben Hyrcanus, the “well that never loses a drop”, was not creative but he had a remarkable memory – not unimportant in the days before the Oral Torah was written in books. Elazar ben Arakh, the “ever-flowing spring,” was creative, but needed to be fed by mountain waters (years later he separated from his colleagues and forgot all he had learned).

Rabban Yochanan ben Zakkai took a Hillel-Rambam view of praise. He used it not so much to describe as to motivate. And that is Lashon tov. Evil speech diminishes us, good speech helps us grow. Evil speech puts people down, good speech lifts them up.

Focused, targeted praise, informed by considered judgment of individual strengths, and sustained by faith in people and their potentiality, is what makes teachers great and their disciples greater than they would otherwise have been. That is what we learn from Rabban Yochanan ben Zakkai.

So there is such a thing as Lashon tov. According to Rambam, it falls within the command of “Love your neighbour as yourself.” According to Avot, it is one way of “raising up many disciples.” It is as creative as lashon hara is destructive.

Seeing the good in people and telling them so is a way of helping it become real, becoming a midwife to their personal growth. If so, then not only must we praise God. We must praise people too.

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