The Book of Beliefs and Opinions by Sa’adiah ben Yosef Gaon

God’s making His creatures’ diligent compliance with His commandments the means of attaining permanent bliss is the better course. For according to the judgment of reason the person who achieves some good by means of the effort that he has expended for its attainment obtains double the advantage gained by him who achieves this good without any effort but merely as a result of the kindness shown him by God. In fact, reason recognizes no equality between these two. This being the case, then, the Creator preferred to assign to us the ampler portion in order that our reward might yield us a double benefit, not merely a compensation exactly equivalent to the effort…

— from The Book of Beliefs and Opinions, Treatise III, Exordium

Sa’adiah ben Yosef Gaon (circa 890–942) was a prominent Egyptian rabbi and Jewish philosopher and is considered the founder of Judeo-Arabic literature. He was also the first Jewish philosopher to systematically integrate Greek philosophy and Jewish theology. A pioneer in Jewish biblical exegesis, he was one of the first to approach the sacred text with a scientific and acutely tuned analytical apparatus, which revealed much about the interrelationship of texts and books. Considered his magnum opus, The Book of Beliefs and Opinions is Gaon’s attempt to present Judaism as a rational body of beliefs.