According to SparkNotes, Moshe the Beadle serves to represent Jewish ideals, values and mysticism throughout the duration of the book "Night." Moshe is Elie's teacher, and in the first few pages, he provides context for Elie's religious conflict.
While Elie struggles with his religion, Moshe's ideals come back to remind Elie that faith is based on asking questions, not on seeking answers. Moshe demonstrates that asking questions shows Elie's continuing faith and commitment to God, not his failure as a spiritual human being. This provides strength for Elie as he continues to witness death and turmoil that cause him to question his faith.