Answer: It makes Eliezer’s later anger toward God more poignant for the reader.
"Night" is a book by Elie Wiesel, published in 1960. In it, Wiesel tells his experience as a prisoner in the Nazi German concentration camps of Auschwitz and Buchenwald in 1944-1945.
One of the major topics in the book is the religious transformation that Wiesel suffers because of his experiences. As the torment he endures goes on, he becomes angry towards God and also doubts Its very existence. He cannot believe a God would allow so much suffering to go on. The first few lines, where he expresses his devotion for the Jewish faith, are meant to highlight the enormity of his transformation, and to show to what extent his experiences destroyed the person that he was before the imprisonment.