In the memoir Night, Wiesel was dehumanized by the Nazis. What are some quotes to prove this?

In Elie Wiesel's Night, the Nazis dehumanize him (and countless others in the concentration camps).

After Elie and his father are separated forever from his mother and his sisters, the horrific acts carried out upon those in the camps destroys everything that Elie thought he knew about the world and strips him of his humanity. Elie was 15 years old when he and his father went into the concentration camp. There are many examples of how Elie became dehumanized.

For example, in the camp, Dr. Mengele and other SS doctors come to take stock of the men. The head of their block tells the men how to avoid being chosen by the doctors to be killed—for example, to run to keep their color high. As Elie and those around him go through the process, each man's prayer is that the doctor will not write down the numbers on his arm. Passing through the check-up, Elie is completely unaware as to whether his number was taken down, and he asks Yossi what happened. Yossi tells him his number was not taken, but it would have been impossible because Elie was running so fast. Yossi and Elie chuckle together; however, we see how Elie has little concern for the others.

I began to laugh. I was glad. I would have liked to kiss him. At that moment, what did the others matter! I hadn't been written down.

On a march in the freezing weather, a young Polish man named Zalman is beside Elie. At one point, while Elie and others force themselves to run forward without the clothing, food or health to sustain such activity, Zalman tells Elie that he cannot go further:

I can't go on any longer. My stomach's bursting...

Elie tries to encourage Zalman, but the man cannot go on, and he sinks to the ground. Elie soon forgets him:

That is the last picture I have of him. I do not think it can have been the SS who finished him, because no one had noticed. He must have been trampled to death beneath the feet of the thousands of men who followed us.

I quickly forgot him...

In order to survive each day, Elie becomes callous in the face of so much death. Prisoners will kill each other over the smallest bit of food. Elie sees a son kill his father to take a small piece of bread from him. Elie does not cringe or cry—survival is all that he can think of.

Towards the end of the novel, Elie and his father become separated when the sirens go off. Waking, Elie notes:

...I remembered I had a father...I had known that he was at the end, on the brink of death, and yet I had abandoned him.

I went to look for him.

But at the same moment this thought came into my mind: "Don't let me find him! If only I could get rid of this dead weight, so that I could use all my strength to struggle for my own survival, and only worry about myself." Immediately I felt ashamed of myself, ashamed forever.

The young man Elie was when he entered the concentration camps died as Elie struggled to survive. In the place of that adolescent appears a man who is hardened in the face of torture and constant death. Elie loses his entire family, even his father who he tries to care for. He loses his faith, and he loses his ability to empathize with what others face. The Nazis strip him of all innocence and kindness in the camps.

Upon learning of his father's death, he cannot even cry. He desperately wants to... "But I had no more tears."

When he is finally liberated from the camp, after his father's death, Elie and other survivors are fed: they only care about food. Some travel to a nearby town to get clothes, but no one thinks of revenge for themselves or their families. Elie becomes seriously ill for two weeks and almost dies. When Elie is finally able to rise from his bed, he goes to look at himself in the mirror, something he had not been able to do since being placed in the ghetto in his hometown of Sighet. 

From the depths of the mirror, a corpse gazed back at me.

Certainly what Elie saw was a reflection of what little of young Elie was left within.