Passover is a festival of redemption, a day when we celebrate our forefathers' exodus from Egypt and the start of their collective journey to the Promised Land.
Nowadays, it is a time when families typically come together around the Seder table, enjoy each other's company and revel in the abundant rituals and symbolism.
But during the Middle Ages, the holiday unfortunately came to be associated with an entirely different theme, one that has bedeviled the Jewish people for nearly nine centuries and has recently been making a bit of a comeback: the infamous blood libel.
It was precisely 870 years ago, in 1144, that the first recorded incident of this slanderous slur in the medieval era took place in England, when the body of 12-year-old William of Norwich was found close to Passover bearing signs of brutal torture.
A local monk named Thomas of Monmouth wrote a book in Latin about the episode three decades later, in which he asserted that the Jews, "collecting all the cunning of their crafty plots," tricked young William, who, "like an innocent lamb, was led to the slaughter."
The monk went on to describe in great detail how "these enemies of the Christian name" tormented their prey, until at last he could no longer endure.
A Jewish convert to Catholicism, Theobald of Cambridge, was quick to corroborate the calumny, falsely claiming that rabbis and Jewish leaders would gather each year in Spain and draw lots to decide in which country they would kill a Christian child to use his blood in ritual practices.
To our modern ears it might sound inconceivable that anyone could possibly believe such nonsense, but the myth succeeded in spreading rapidly across Europe.
And as the late Joshua Trachtenberg pointed out in his seminal work, The Devil and the Jews: The Medieval Conception of the Jew and Its Relation to Modern Anti-Semitism, ritual murder accusations against the Jews had a profound influence on public opinion.
"Crowning the diabolical conception of the Jew," Trachtenberg wrote, "it rendered him a figure of such sinister horror even in that blood-stained, terror-haunted period that it is little wonder that common folk came to despise and to fear and to hate him with a deep fanatical intensity."
While the Norwich incident did not result in any known attacks against Jews, the first instance of the blood libel to take place in France nearly 30 years later proved far more deadly.
In 1171, the Jewish community of Blois was accused of crucifying a Christian child for Passover and tossing his body into a local river.
The entire community was imprisoned and then sentenced to be burned to death. When the Jews were taken to the auto-da-fe, they were told they could save themselves by converting, but nearly all of them refused to do so, preferring to die and sanctify God's name.
As the flames engulfed them, the Jews of Blois could be heard singing the "Aleinu" prayer, which underlines the distinction between Israel and the nations, as well as the belief in one God.
Rather quickly, the blood libel and ritual murder accusations began to be hurled against the Jews in a spate of other countries across the European continent at various times of year, often invoking different themes.
Hence, for example, when five Christian children were found dead in the German city of Fulda in December 1235, the Jews were accused of having killed them in order to use their blood for medicinal purposes. As a result, 34 Jewish men and women were murdered by Crusaders.
A sign of just how popular the blood libel was in the public's imagination can be found in The Canterbury Tales, Geoffrey Chaucer's 14th-century literary classic.
Though it was written nearly 100 after King Edward I expelled English Jewry in 1290, it contains a passage that is chilling in its hateful depiction of Jews.
In the Prioress's Tale, Chaucer writes that after a Christian child sings a hymn, "the Serpent Satan that has his wasps' nest in Jews' hearts," inspires them to abduct and murder the child and cast his body into a pit, "where these Jews purge their entrails."
Throughout the subsequent centuries, from Spain to Hungary, Jewish communities were repeatedly victimized by such spurious allegations, often resulting in the spilling of a great deal of innocent Jewish blood.
Even in the 19th century, there was a series of infamous libel episodes, such as the Damascus affair in 1840, when Jews were blamed for the murder of a Capuchin monk and his servant.
And in 1911, a Russian Jew named Menahem Mendel Beilis living in Kiev was arrested and accused of ritually murdering a 13-year-old boy and mutilating his body. He was put in trial in 1913 and acquitted after the prosecution's case fell apart.
Needless to say, the Nazis did not hesitate to revive the blood libel, using its imagery throughout the 1930s to further stoke the flames of German hatred for the Jews.
EVEN IN our modern, more progressive era, the lie continues to live on. And whereas the libel was once primarily the domain of Christendom, nowadays it is frequently invoked by Israel's Arab foes.
In May of last year, as the Middle East Media Research Institute revealed, an Egyptian politician named Khaled Zaafrani said the following during a television interview: "it is well-known that during Passover they make matzos called the 'Blood of Zion.' They take a Christian child, slit his throat, and slaughter him… they never forgo this rite."
In addition, the website belonging to a Palestinian organization started by Hanan Ashrawi published an article in March 2013 criticizing US President Barack Obama for hosting a Passover Seder, which read as follows: "Does Obama in fact know the relationship, for example, between 'Passover' and 'Christian blood'?! Or 'Passover' and 'Jewish blood rituals?!'" Furthermore, noted the article, "much of the chatter and gossip about historical Jewish blood rituals in Europe are real and not fake as they claim; the Jews used the blood of Christians in the Jewish Passover."
Subsequently, after coming under heavy criticism, the article was taken down.
Of course, anyone who takes even a cursory glance at the Torah's explicit prohibition against consuming blood, and the Sages' warnings against it, would quickly grasp the absurd nature of the blood libel allegations.
Nevertheless, this vicious canard has continued to haunt our people for much of its modern existence.
As we celebrate our deliverance on Passover, what are we to make of all this? Perhaps the most inspired and comforting answer to this conundrum was provided by none other than Zionist thinker and writer Ahad Ha'am.
In one of his essays, he seizes upon the world's acceptance of the blood libel and turns it into a source of consolation for the beleaguered people of Israel. "Every Jew," he wrote, "who has been brought up among Jews knows as an indisputable fact that throughout the length and breadth of Jewry, there is not a single individual who drinks human blood for religious purposes. 'But' – you ask – 'is it possible that everybody can be wrong, and the Jews right?' Yes, it is possible: the blood accusation proves it possible. Here, you see, the Jews are right and perfectly innocent."
Although written nearly a century ago, Ahad Ha'am's words remain as resonant as ever.
For at a time when Israel's legitimacy and very existence are increasingly questioned, and the specious propaganda of our foes is so readily believed, the history of the blood libel does indeed remind us of an important truth: Our cause is just, even if the world may think otherwise.