In 1983, Tlass wrote and published "The Matzah of Zion", which is a treatment of the Damascus affair of 1840 that repeats the ancient "blood libel", that Jews use the blood of murdered non-Jews in religious rituals such as baking Matza bread. In this book, he argues that the true religious beliefs of Jews are "black hatred against all humans and religions," and that no Arab country should ever sign a peace treaty with Israel. Tlass re-printed the book several times, and stands by its conclusions. Following the book's publication, Tlass told "Der Spiegel", that this accusation against Jews was valid and that his book is "an historical study ... based on documents from France, Vienna and the American University in Beirut."