Soon afterward he was obliged to enter upon a new contest with a disciple of the convert Abner of Burgos, with whose writings, especially with his Mostrador de Jeosticia, Moses was thoroughly acquainted.
In 1374, at the desire of the members of his community, he wrote, in the form of a dialogue between a Jew and a Christian, the main substance of his debates, which treated of the Trinity, of the virginity of Mary, of sacrifice, of the alleged new teachings of Jesus and of the New Testament, of the seven weeks of Daniel, and of similar matters.
His book, which is divided into seventeen chapters, dealing with 125 passages emphasized by Christian controversialists, is entitled "'Ezer ha-Emunah" (The Support of Faith אמונה).
It was sent by its author to David ibn Ya'ish at Toledo, and manuscripts of it are found at Oxford, Berlin, Parma, Breslau, and elsewhere.
[1][2] Isidore Loeb (1888) showed that Moses ha-Kohen followed on from the pioneering works such as Shem Tov Shaprut's The Touchstone, Joseph Kimhi's Sefer ha-berit and most of all Jacob ben Reuben's Milhamot ha-Shem.