Answer:
He believes he has an obligation to share his experiences.
Step-by-step explanation:
The reason Elie Wiesel gives for writing his story is that "He believes he must share his experiences."
Elis Wiesel, a Romanian American writer who was widely known for his book titled "Night," expressed in the book's preface that the reason he is telling his story is to ensure the atrocities and criminal activities of the Nazis did not go down unrecorded. That is to make sure the Nazi did not score any political point; he needs to voice out and share his experience.