Moreover, Halevy was committed to finding people who had left Judaism, and return them to the Jewish faith. He fought zealously against Jewish assimilation and conversion to Islam and to the Baháʼí Faith, which was popular at this time. Under his influence many converts, mainly from Mashhad, returned to Judaism. For that he was recognized by the Alliance Israélite Universelle in Paris. He dedicated all his efforts for this purpose, writing pamphlets, giving sermons, Sabbath after Sabbath, in the synagogue, and establishing various societies with the purpose of saving and returning the lost souls from their forced conversion back to Judaism.