Musar su Ecclesiaste 3:20

To what can this be compared? To [the instance of] a wealthy man, a merchant in precious gems, who, journeying from home, asks one of his companions to take care of his possessions, permitting him first to see his beautiful gems. Upon opening the chest, he sees them, and, beside them rotted earth. At this, he says to himself: "This wealthy one is a fool! How can he leave rotted earth together with such beautiful jewels!" The analogue is self-explanatory. Is it not obvious that all the dead things of the world, in the course of years, all turn to dust, both he himself and all the things he yearned for in his lifetime, as it is written (Koheleth 3:20): "All came from dust and all returns to dust." And he will be astonished at himself forever. How could he have combined in his chest [i.e., in his heart] two loves together? Love of the L-rd and His Torah, the true gems, more desirable than gold and fine gold, and the love of dust — together! Did he not know in his lifetime that in the end all would return to dust? Therefore, one must take great care to drive out of his mind, thoughts of lust for the desires of the world. This is the intent of "And make our hearts one … and let us not be ashamed, forever." And this is the intent, in the recital of Shema, of (Devarim 6:5): "And you shall love the L-rd your G-d with all your heart, etc."