Musar su Salmi 36:9

And through it [Torah study] one merits the world to come, as Chazal have said (Peah 1:1): “These are the things … and Torah study over and against all.” And Chazal have said (Bava Metzia 85b): “That which is written (Iyyov 3:19): ‘The small and the great are there [in the next world], and the servant free of his master.’ Do we not know that the small and the great are there? — [The intent is] rather, that all who make themselves small for Torah in this world are made great in the world to come, and all who make themselves servants for Torah in this world are made free men in the world to come.” And in Avoth 6:3: “There is no honor but Torah, as it is written (Mishlei 3:35): ‘The wise will inherit honor.’ Do not desire more honor than your learning and do not lust for the table of kings. For your table [in the world to come] is greater than their table in this world, and your crown is greater than their crown, etc.” And in Sanhedrin 100a: “All who blacken their faces in Torah study in this world, the Holy One Blessed be He brightens them in the world to come, as it is written (Song of Songs 5:15): ‘His countenance is as Levanon, choice as the cedars.’” And, similarly, in Midrash Rabbah: “R. Yehudah interpreted the verse as relating to Torah scholars. One verse states (Ibid. 11) ‘black as a raven,’ and another (Nachum 2:5): ‘Their appearance is like flames, they flash like lightning.’ These are the Torah scholars, who look ungainly and black in this world but whose appearance is flamelike in the next world.” R. Tanchum ben Chanilai said: ‘All who starve themselves for words of Torah in this world, the Holy One Blessed be He sates them in the world to come, as it is written (Psalms 36:9): ‘They will be sated with the fatness of Your house.’”

Therefore, every man who reflects should try with all his might to attain the final good, for if a man reaches a good state or elevation then he will always desire to ascend to the degree which is higher until he will finally attain the ultimate good and in this manner he will reach the "world of reward" which is the world to come. Long ago David longed to attain the good of the world to come, when he said: "Oh, how abundant is Thy goodness, which Thou hast laid up for them that fear Thee" (Ps. 31:20), and he said: "They are abundantly satisfied with the fatness of Thy house, and Thou makest them drink of the river of Thy pleasures" (Ps. 36:9). And this degree no one can attain except he be worthy of it, as he said: "Who shall sojourn in Thy tabernacle? Who shall dwell upon Thy holy mountain? He that walketh uprightly, and worketh righteousness" (Ps. 15:1). And the rest of the matter which is said there.