(1) The foundation of piety and the root of perfect service [of G-d] is for a man to clarify and come to realize as truth what is his obligation in his world and to what he needs to direct his gaze and his aspiration in all that he toils all the days of his life.
(2) Behold, what our sages, of blessed memory, have taught us is that man was created solely to delight in G-d and to derive pleasure in the radiance of the Shechina (divine presence). For this is the true delight and the greatest pleasure that can possibly exist. The place of this pleasure is, in truth, in Olam Haba (the World to Come). For it was created expressly for this purpose.
(3) But the path to arrive at the "desired haven" (Ps. 107:30) of ours is this world. This is what our sages of blessed memory said: "this world is like a corridor before the World to Come" (Avot 4:16).
(4) The means that lead a person to this goal are the commandments which the blessed G-d commanded to us. The place of the performance of these commandments is only in this world. Therefore, man was first placed in this world so that through these means prepared for him here, he will be able to reach the place prepared for him, namely, the World to Come, there to be sated with the good which he acquired through these means. This is what our sages of blessed memory said "today to do them, and tomorrow to receive their reward" (Eruvin 22:1).
(5) When you look further into the matter, you will see that true perfection lies only in clinging to G-d. This is what King David said "But as for me, closeness to G-d is my good" (Ps. 73:28) and, "one thing I asked from G-d; that I seek, that I may dwell in G-d's house all the days of my life, to gaze on the pleasantness of G-d..." (Ps. 27:4). For only this is the good, while anything besides this that people consider good is really emptiness and mistaken worthlessness.
(6) For a person to attain this good, it is proper that he first exert himself strenuously to acquire it, namely, to exert himself to cling to the blessed G-d through the power of deeds whose consequence is this end. These deeds are the commandments.