That tradition is now widely acknowledged to be incorrect. First, the condition described in the Torah simply does not fit the symptoms of leprosy. Second, the Torah applies it not only to various skin conditions but also to mildew on clothes and the walls of houses, which certainly rules out any known disease. The Rambam puts it best:

“Tsara’at is a comprehensive term covering a number of dissimilar conditions. Thus whiteness in a person’s skin is called tsara’at. The falling off of some of his hair on the head or the chin is called tsara’at. A change of colour in garments or in houses is called tsara’at.”

Hilchot Tumat Tsara’at 16:10

Seeking to identify the nature of the phenomenon, the Sages sought for clues elsewhere in the Torah and found them readily available. Miriam was smitten by tsara’at for speaking badly about her brother Moses (Num. 12:10). The Torah later gives special emphasis to this event, seeing in it a warning for all generations:

“Be careful with regard to the plague of tsara’at . . . Remember what the Lord your God did to Miriam along the way after you came out of Egypt.”

Deut. 24:8-9

It was, in other words, no normal phenomenon but a specific Divine punishment for lashon hara, evil speech. The Rabbis drew attention to the verbal similarity between metzora, a person afflicted by the condition, and motzi shem ra, someone guilty of slander.

Rambam, on the basis of rabbinic traditions, gives a brilliant account of why tsara’at afflicted both inanimate objects like walls and clothes, and human beings:

It [tsara’at] was a sign and wonder among the Israelites to warn them against slanderous speaking. For if a man uttered slander, the walls of his house would suffer a change. If he repented, the house would again become clean. But if he continued in his wickedness until the house was torn down, leather objects in his house on which he sat or lay would suffer a change. If he repented they would again become clean. But if he continued in his wickedness until they were burned, the garments which he wore would suffer a change. If he repented they would again become clean. But if he continued in his wickedness until they were burned, his skin would suffer a change and he would become infected by tsara’at and be set apart and alone until he no more engaged in the conversation of the wicked which is scoffing and slander.

Hilchot Tumat Tsara’at 16:10

The most compelling illustration of what the tradition is speaking about when it talks of the gravity of motsi shem ra, slander, and lashon hara, evil speech, is Shakespeare’s tragedy Othello. Iago, a high-ranking soldier, is bitterly resentful of Othello, a Moorish general in the army of Venice. Othello has promoted a younger man, Cassio, over the more experienced Iago, who is determined to take revenge. He does so in a prolonged and vicious campaign, which involves among other things tricking Othello into the suspicion that his wife, Desdemona, is having an adulterous affair with Cassio. Othello asks Iago to kill Cassio, and he himself kills Desdemona, smothering her in her bed. Emilia, Iago’s wife and Desdemona’s attendant, discovers her mistress dead and as Othello explains why he has killed her, realises the nature of her husband’s plot and exposes it. Othello, in guilt and grief, commits suicide, while Iago is arrested and taken to be tortured and possibly executed.

It is a play entirely about the evil of slander and suspicion, and portrays literally what the Sages said figuratively:

“Evil speech kills three people: the one who says it, the one who listens to it, and the one about whom it is said.”

Arachin 15b

Shakespeare’s tragedy makes it painfully clear how much evil speech lives in the dark corners of suspicion. Had the others known what Iago was saying to stir up fear and distrust, the facts might have become known and the tragedy averted. As it was, he was able to mislead the various characters, playing on their emotional weaknesses, distrust and envy, getting each to believe the worst about one another. It ends in serial bloodshed and disaster.

Hence the poetic justice Jewish tradition attributes to one of the least poetic of biblical passages, the laws relating to skin diseases and mildew. The slanderer spreads his lies in private, but his evil is exposed in public. First the walls of his house proclaim his sin, then the leather objects on which he sits, then his clothes, and eventually his skin itself. He is condemned to the humiliation of isolation:

‘Unclean! Unclean!’ he must call out . . . Since he is unclean, he must remain alone, and his place shall be outside the camp.

Lev. 13:45-46

Said the Rabbis: Because his words separated husband from wife and brother from brother, his punishment is that he is separated from human contact and made an outcast from society (Arachin 16b).

At its highest, WikiLeaks aims at being today’s functional equivalent of the law of the metzora: an attempt to make public the discreditable things people do and say in private. The Sages said about evil speech that it was as bad as idolatry, incest, and murder combined, and it was Shakespeare’s genius to show us one dramatic way in which it can contaminate human relationships, turning people against one another with tragic consequences.

Never say or do in private what you would be ashamed to read about on the front page of tomorrow’s newspapers. That is the basic theme of the law of tsara’at, updated to today.