Mention of the World to Come in the Torah

Q: Why doesn't the Torah explicitly mention the World to Come?
A: Maran Ha-Rav Kook says in his book Orot Ha-Torah (5, 8) that man has a propensity for lofty spiritual matters. If we discuss the World to Come too much, people will dream about it and abandon this world, and as a result will not merit life in the World to Come. But it certainly needs to be mentioned, and it is therefore mentioned in hints. Only afterwards, when groups such as the Tzedukkim, who did not believe in the World to Come, arose within the Nation, did our Rabbis need to emphasize this matter in order to bring it into proper perspective. The way of the Torah is not to discuss broad theological issues but to leave them as basic principles. However, when these principles are challenged, they have to be explicitly discussed. And this is what our Sages did. We must therefore exert our effort in this world and not focus too much on the World to Come.