Source for Afterlife
I know that Judaism believes in the afterlife, but in reading the Torah I did not see any mention of that. You would think such major, essential, fundamental ideas would be openly stated. Where is this discussed?
The Aish Rabbi Replies
Maimonides writes (Teshuva 8:1) that we know of this from the Torah's statement in Deuteronomy 22:7: "You will have good and your days will be long." Without the traditional interpretation we could think it is just promising long life in this world. Elsewhere, Maimonides also mentions Numbers 24:17-18 and Deuteronomy 30:3-5.
The afterlife is discussed in detail in the Talmud, Sanhedrin Chapter 11.
Another source for the afterlife is logic: The soul, which is spiritual and therefore cannot die or decay, existed in the “world of souls” before the body was “born,” and will continue to exist after.
The reason the afterlife is not mentioned explicitly in the Torah, is because the purpose of earthly existence is to do good in this world, to give the soul a chance to elevate itself. To the extent we make the right "spiritual" choices (e.g. give charity, care for others, pray, study Torah) is the extent that we become sensitive to the spiritual reality of God. This attunes our soul to appreciate the pure spirituality of the eternal afterlife.
The famous book Path of the Just explains that the purpose of life is to enjoy God's radiance. Rabbi Noah Weinberg explains that this refers to the pleasure we get in this world from doing good. The eternal reward will come of its own accord, providing that we do good in this world. Further, the eternal reward is perhaps too intangible to be an effective motivator.
Finally, the ultimate reason for serving God and doing His mitzvot is so that we can become close to God, love and admire His essence. Thus, we should serve God whether or not there is a reward or punishment, either here or in the afterworld. (source: Maimonides - Mishnah Sanhedrin 10; Chatam Soffer Y.D. 356)