Why God Hid the Reward of Each Commandment in the Torah

AND IT SHALL COME TO PASS, IF YOU HEED (Deuteronomy 7:12). This is what Scripture says (Proverbs 5:6): SHE DOES NOT WEIGH THE PATH OF LIFE; HER WAYS WANDER, AND SHE DOES NOT KNOW IT. [Rabbi Abba bar Kahana said:] You should not engage in give-and-take among the commandments of the Torah, considering which reward of a Torah-precept or commandment is greater, and then perform that one. Why? HER WAYS WANDER, AND SHE DOES NOT KNOW IT: the paths of the Torah are made to shift about. Rabbi Hiyya said: A parable. To what is the matter comparable? To a king who had an orchard, and he brought workers into it, but the king did not reveal to them the wage for his plantings; for had he revealed to them the wage for his plantings, one would see which planting's reward was greater and plant that one, and the work of the orchard would be found partly neglected and partly carried out. So too the Holy One, blessed be He, did not reveal in the Torah the reward of each and every commandment; for had He revealed it, the commandments would be found partly carried out and partly neglected. And Rabbi Aha, in the name of Rabbi Abba bar Kahana, said: The Holy One, blessed be He, made the reward of one who performs commandments shift about in this world, so that Israel would perform them in full.