Rabbi Yavetz was born in Spain and left there during the Expulsion in 1492. He finally settled in Mantua, Italy, and assumed an honored place in the community.
He was absorbed with the meaning of the Spanish Expulsion and why it occurred, and wrote an entire treatise, Ohr HaChaim, in which he provided his interpretation. According to R. Yavetz, the catastrophe resulted from Spanish Jewry’s preoccupation with philosophy and secular knowledge which became their central focus, whereas Torah and mitzvot no longer were the primary purpose of their lives. He was not opposed to knowledge per se, but rather to the fact that it had supplanted Torah and mitzvot in importance.
R. Yavetz testifies that only one in a hundred philosophers is preoccupied with Torah and mitzvot, and even those few are ambivalent. And in an oft quoted passage points out that the Jewish philosophers were the first to convert, whereas the simple folk, imbued with simple faith, refused to succumb. He quotes approvingly from R. Hai Goan, “those who say to you that one will attain knowledge of Torah through philosophy, do not listen to them and know that they have falsified the truth, for you will not find fear of sin, alacrity, modesty and holiness except among those who are preoccupied with Mishnah and Talmud”.
He studied Maimonides’ Guide with Abravanel whom he considered to be the finest interpreter of that work, but states that after Abravanel would provide an excellent explanation of the Guide he would add: “this is the meaning of Rabbeinu Moshe but not the intention of Moshe Rabbeinu”.
R. Yavetz became increasingly interested in Kabbalah and encouraged R. Yehuda Chait, who was expelled from Lisbon and suffered terribly until he reached Mantua, to compose a classic Kabbalistic commentary. According to R. Yavetz, there are only three articles of faith, all derived from the passage “I shall be what I shall be” (Exodus 3:14), Creation of the World, Providence and Divine Unity, and Redemption under which he subsumed the thirteen principles of Maimonides.
He wrote Chasdai HaShem, Maamar HaAchdut and Yesod HaEmunah. He also wrote commentaries on Psalms and the Ethics of the Fathers. The latter work is extremely popular to this day. The great Chassidic sage, R. Tzvi Elmelech of Dinav, wrote an extensive commentary, Mayan Ganim, on the Ohr HaChaim. Besides the above printed works, R. Yavetz left many unprinted manuscripts.