Rabbi David Fox Sandmel, chair of the International Jewish Committee for Interreligious Consultations, sent greetings to the 31 August to 8 September assembly, meeting in the southern German city with the theme "Christ's love moves the world to reconciliation and unity."
Sandmel noted that the Hebrew month of Elul began last weekend.
"Elul is a special time of spiritual and moral preparation for the Ten Days of Repentance, beginning with the Jewish New Year and concluding with the Day of Atonement," he said.
"The theme of this assembly is reconciliation that leads to unity."
He explained that essential to the Jewish understanding of repentance is the imperative of reconciliation.
"During Elul, Jews are urged to examine ourselves, to confront our moral failings, confess them before God, and ask for forgiveness. We are explicitly instructed to seek out whomever we have wronged, to make amends, and to seek their forgiveness."
Reconciliation between people
Sandmel said that Jewish tradition teaches that "reconciliation between people is a prerequisite for forgiveness from God."
He said that when humanity is reconciled with God and their neighbours, it reunites on both the human and the divine levels.
"One of the most profound examples of the power of communal reconciliation can be seen in what has taken place between Jews and Christians since the end of the Shoah, the Holocaust," Sandmel said in the message.
"The repudiation by many Christians theologians and institutions of antisemitism and the rejection of the classical Christian ‘teaching of contempt' for Jews and Judaism is unprecedented in human history.”
Sandmel said that at its founding in 1948, the WCC called antisemitism a "sin against man and God" and repeatedly spoken out against anti-Jewish rhetoric and violence.
He said that "this revolution in Jewish-Christian relations should be celebrated and can inspire and serve as a model that prejudice and hatred can be overcome.
"Many in the Jewish community are sadly unaware of the great progress in Jewish-Christian relations," said Sandmel.
The International Jewish Committee for Interreligious Consultations is a consortium of 11 major international Jewish organizations engaging with other international religious bodies, including the WCC, the Vatican, World Evangelical Alliance, Ecumenical Patriarchate, and non-Christian organizations.
Greetings by Rabbi David Fox Sandmel to the WCC 11th Assembly in Karlsruhe
Livestream of the WCC 11th Assembly in Karlsruhe, Germany