Given the unspeakable horrors inflicted upon the inmates of Auschwitz by their Nazi captors—death, violence, degradation, and unimaginable suffering—it's perhaps only natural that a number of them will start to question their most fundamental religious beliefs.
Over the course of the book, men who had previously been steadfast in their faith will come to question the very existence of God. They want to know why God has apparently turned his back on his chosen people and allowed them to suffer so appallingly.
Elie is one of them. When he arrived at Auschwitz, he was still quite a devout young man with a firm commitment to Judaism. But as horror piles upon horror, his faith gradually starts to ebb away until it vanishes completely.
The general condition of life in Auschwitz is enough to separate men from their faith. But sometimes it takes specific incidents to do this. The most significant of these incidents, not to mention the most tragic and horrific, concerns the execution by hanging of a young boy.
The boy, who is described as looking like a sad-eyed angel, has been condemned to death by the SS for possessing arms. His subsequent execution is a truly horrible affair. He isn't just hanged; he's slowly strangled to death, ensuring that his last moments on earth are filled with agonizing pain and suffering.
The other inmates are forced to watch this evil spectacle. As they do, it soon becomes clear that the relationship between God and some of his worshippers has changed completely. A man behind Elie shouts
Where is merciful God, where is He?
He then demands to know
For God's sake, where is God?
As Elie watches this horrifying act of murder slowly unfold before his eyes, he thinks he knows the answer to these questions; God is there, hanging from the gallows. The relationship between God and the once-devout Elie has changed forever and there's no going back to how things used to be.