Wagner never quoted Mendelssohn's Reformation Symphony in Parsifal. They both quoted the musical sequence known as the 'Dresdner Amen', which was composed at least 20 years before Wagner's birth by Naumann (1741-1801). The tune was immensely popular and recognizable during the first half of the 19th century; Bruckner and Mahler also used it.
U.S. House Speaker Boehner brushes off call for his ouster (Reuters)
from the article: Wagner didn't hate all Jews, just 'bad' ones, argues Israeli scholar