Akiba Drumer makes a simple request to his fellow inmates: that they say the Kaddish for him after his death. In Judaism, the Kaddish is a hymn of praise often sung after someone has died. It is this “Mourner's Kaddish” that Akiba wants to be sung after he passes away.
Akiba makes this request despite the fact that his faith has gone. One day, he tells Elie,
It's over. God is no longer with us.
Akiba had previously been such a devout Jew, believing with every fiber of his being that the evils inflicted upon the Jews by the Nazis were all part of a test to see if God's chosen people were capable of overcoming their base instincts. But now, after everything he's been through, he's convinced that God has abandoned the Jews just when they need him the most.
Even so, he still asks the other inmates to say Kaddish for him when he dies. Elie and the others promise that they will do so. However, three days after Akiba's death, everyone forgets to say Kaddish.
The reason for their forgetfulness isn't hard to find. During those terrible days, the inmates received more blows than food as they were forced to carry out crushing toil. Focused solely on the grim fight for survival, they had other things on their mind than saying Kaddish for Akiba.