Adar Joy-In A Mitzvah
The Talmud states: it is written, “And I praised joy (Ecclesiastes 8:15),” and it is also written, “and as to joy, what does it achieve (2:2)?” The contradiction is only on the surface. The answer is: the former verse deals with the joy of a mitzvah; it is this to which “I praised joy” applies. The verse, “and as to joy, what does it achieve,” applies to joy which is not related to a mitzvah.
It is known that the reward of a mitzvah is another mitzvah, and the reward of a transgression is another transgression. Thus it is written, “and I praised joy,” which signifies only the joy of a mitzvah which is the mitzvah itself. The reward of the mitzvah draws forth an additional mitzvah; whereas, “as to joy, what does it achieve,” does not activate an additional force for good. Joy in the mitzvah, however, creates further joy, for it is derived from the aspect of the soul which is called “Abraham.” The difference between the two is as follows: “Abraham gave birth to Isaac [he will laugh] (Genesis 25:19),” to add further laughter and joy, whereas sorrow follows the joy that is unrelated to a mitzvah, as is stated in the Zohar (Midrash haNe’elam; Toledot 135a). But the joy of a mitzvah generates further joy. (Toledot Yaakov Yosef; Toledot)