In 1942, Rabbi Azriel David Fastag, a cantor composer from the Modzitz hasidic sect, was squashed onto a train together with thousands of his Jewish brethren, on their way to the Treblinka death camp.
In the suffocating crush, he began humming a quiet tune to the words of the twelfth Principle of Faith, "I believe with full faith in the coming of Moshiach (the messiah)." The tune spread throughout the train car, becoming a tune of hope in the darkness.
Rabbi Azriel David, who sensed his end was near, asked that the tune be passed to his leader, the Modzitz Rebbe, who then lived in the US. He promised half of his portion in the World to Come to whoever succeeded in bringing the tune to the Rebbe.
Two Jews jumped from the train. One of them was killed, but the second succeeded in teaching the tune to the Modzitz Rebbe, Rabbi Shaul Yedidya Elazar Taub, who disseminated it throughout the Jewish world.
"With this tune, Jewish marched to the gas chambers, and with this tune, Jews will march to greet Moshiach," he said.
The tune became a symbol of hope and faith, and is performed to this day at Holocaust memorial events and ceremonies.