One of the greatest scholars and main pillars of Judaism during the dark period of the Jewish persecutions in Spain, was Rabbi Hasdai, the son of Rabbi Judah Crescas.

Rabbi Hasdai Crescas was born in Barcelona, Spain, in the year 5110 (1340), in a noble family that had been famous for its scholars and leaders in Jewry for generations. At an early age he proved himself worthy of his noble family. He was blessed with an unusually sharp and clear mind, and with an iron will to learn everything possible of the Torah and Talmud. He was soon sent to Gerona, then the seat of a famous academy of the Talmud, headed by the most famous Talmudist of that time, Rabbi Nissim Gerondi (of Gerona), better known as the RaN, the author of the commentary on the RIF (Rabbi Isaac Alfasi). In Gerona Rabbi Hasdai studied together with another great student of the Talmud, Rabbi Isaac ben Sheshet, the famous RIBaSH, author of many decisions (Responsa) regarding the Talmud and practical Jewish law.

In the year 1367 a wave of cruel persecution broke out in Barcelona, when the Jews were accused, falsely of course, that they had desecrated religious articles of the Church. King Pedro IV of Aragon ordered the arrest of Rabbi Nissim and Rabbi Hasdai and other important Jews, who were thrown into the Barcelona prison. Although their innocence was clear from the start, and was soon proved also in Court, they were kept in prison for several months, and were released only after a large sum of money was paid as "bail." After his release Rabbi Hasdai Crescas moved to another city in Spain, Saragossa, where he spent the rest of his life.

Rabbi Hasdai was welcomed with great honor by the Saragossa Jewish community, and was even offered the position of Chief Rabbi. However, Rabbi Hasdai did not accept the position, wishing to devote his time to his studies. Nevertheless he was always ready to offer his services, advice and the fruits of his learning to his brethren. The Jews of Saragossa, and of many other cities, turned to him frequently in all their difficulties. But not the Jews alone, for his wisdom and uprightness were admired also by the royal houses of Aragon and Navarra, and he was often called upon to undertake diplomatic missions for them.

Many young scholars came to Rabbi Hasdai to study under his guidance. Among them were Rabbi Joseph Albo, who became a famous philosopher, and Rabbi Isaac Duran, who also wrote important philosophical works in defense of Judaism against the attacks of Christian clergymen.

Another wave of persecution burst upon the Jews of Spain in the year 1391. Rabbi Hasdai's son who had gone to Barcelona to bring his bride home, was caught in the mob attacks on the Jews, and was murdered together with many thousands of other Jews. Many other Jews were forced to accept the Catholic faith. In a letter to the Jewish communities of Avignon and other cities in the South of France, Rabbi Hasdai describes these terrible mob attacks, instigated by fanatical monks. Thanks to his influence, the Jewish community of Saragossa was spared the tragic fate of other Jewish communities in Spain.

Hatred of the Jews was continually fanned by the Dominican Vincent Ferrer, the apostate (converted Jew) Paulos of Burgos, and others. At the same time, missionaries were active among the upper classes of the Jews trying to influence them to accept Christianity through "learned" arguments and the threat of violence.

Rabbi Hasdai wrote a treatise in Spanish to show why a Jew had no reason to give up his faith under any circumstances. Unfortunately, the original of that work was lost, but an important part. of it was preserved in Hebrew translation by Rabbi Joseph ibn Shemtov. It was called "Bittul Ikrei Hanotzrim," meaning "refutation (denial) of the Christian doctrines. It proved very helpful to many Jews in finding answers to the missionary arguments, and strengthened many a Jewish spirit.

The most important scholarly work of Rabbi Hasdai Crescas is his "Or Hashem," the Light of G‑d. In this work he states his views and principles of faith. He does not agree with other philosophers, that only through knowledge and intellectual searching can man come closest to G‑d. The human mind, Rabbi Hasdai declares, is too limited and cannot arrive at the knowledge of G‑d no matter how great is his mind. Rather through the love of G‑d and the fulfillment of His commands can man come closest to G‑d. Rabbi Hasdai also points out the mistakes in the philosophy of Aristotle which was so admired by philosophers in those days. Naturally, such views as Rabbi Hasdai expressed in his "Or Hashem" were not too popular in those days, and this is perhaps the reason why his work was not as widely quoted as the "Ikarim" of his disicple Rabbi Joseph Albo. Nevertheless, his work has greatly influenced Jewish thought for centuries, and has strengthened Jewish loyalty to the Torah and Mitzvoth. Rabbi Isaac Abarbanel, a great scholar and philosopher of later years, greatly praised Rabbi Hasdai's work. Rabbi Jacob ben Habib, compiler of the famous work "Ein Yaakov," (Fountain of Jacob), with Aggadic selections from the entire Talmud, was also a great admirer of Rabbi Hasdai's work and used parts of the "Or Hashem" in his work. "Sweeter than honey," he says of Rabbi Hasdai's words of wisdom.

Rabbi Hasdai Crescas lived up to his doctrines that "the greatest human good is the spiritual perfection attained through love of G‑d and adherance to the Torah," for he was indeed a saintly and pious man, who spread the Light of G‑d in the dark ages of our Exile.