"The need we have to memorialize the dead is essential to human nature," he said.
He went on to tell the story of his father-in-law, Sara's father: Shmuel.
"Shmuel escaped from the Shoah because he was a fierce pioneer," making aliyah in 1933.
"We told him, 'Go back, visit your hometown Bilgoraj [Poland].' He never went back. He didn't want to go back, he wanted to retell."
Shmuel went on to become a Tanach scholar, educator and poet, and was even invited by David Ben-Gurion to his first Tanach course.
"He retold [of his life before Israel] through his beautiful and provoking poems," Netanyahu said, adding that he reads one every year on this day.
Mezritch was "a college town of yeshivas, batei midrash, and synagogues." Jews had lived in Mezritch for at least four centuries.
The Novardok Yeshiva, established in 1896, is considered one of the most important yeshivas in pre-World War II, a bastion of the Mussar movement, adding up to a network of hundreds of yeshivas.
Shmuel died at the age of 97.
He and his wife, Hava, had four children.
Netanyahu ended his speech be telling of the last wishes of his father-in-law, which was to have the names of his perished family members engraved on his tomb.
He then read all the names off for the crowd: "May the memories of our brothers and sisters who perished in the Holocaust be remembered forever in our souls and in our memories.