The Maor VeShemesh (Behaloscha) writes, "A great foundation in avodas Hashem is to distance oneself from שחורה ומרה עצבות, from being sad, as far as one possibly can because the Zohar says that atzvus is like avodah zarah (זרה עבודה שמץ). The proof is that when one is sad, he has thoughts of avodah zarah. Therefore, one must be very distant from atzvus. It can lead to all aveiros."
The Tanya (Igeres HaKodesh ch.11) also teaches that sadness is like avodah zarah, and he explains that this is because sadness means he doesn't believe that everything is for the good. He writes, "When one is sad, this means he thinks his life isn't perfect and is lacking something he needs. But to think so is kefirah, heresy, chas veshalom. Therefore, the chachamim of kabbalah warn against atzvus immensely..."
So, this week, when we seek to cleanse ourselves from all aspects of avodah zarah, it is an excellent time to strive to be happy and to cleanse ourselves from atzvus.
The renowned maggid of Yerushalayim, Reb Sholom Schwadron zt'l, would use humor in his drashos to help bring out mussar points. Once, during his weekly Friday night drashah in the Zichron Moshe Shtiblach, a person got up and announced, "This is leitzanus, light-headedness. It is improper to speak this way."
Reb Sholom took the rebuke to heart. He feared that perhaps this man was right, so he went to the Chazon Ish for advice. The Chazon Ish asked for a demonstration so that he could decide whether he should continue speaking in his humorous fashion. Reb Sholom wanted the Chazon Ish to experience his drashos, so he demonstrated his manner of speech as if he were speaking before a large audience. The performance found favor in the Chazon Ish's eyes, who laughed and said he should continue speaking this way. He explained, "In Lithuania, there was a lot of yiras Shamayim, but the joy was by the maskilim, and that is why so many youths fell away." This story is another indication of the importance of joy and how the lack of it can result in heresy or avodah zarah, r'l. When there is happiness by us, children won't look for happiness in other places.
The women didn't sin by the egel. Rebbe Yissachar Dov of Belz zt'l explains that this is because the women danced at kriyas Yam Suf, as it states (Shemos 15:20), אחות הנביאה מרים ותקח בתפים אחריה הנשים כל ותצאנה בידה התוף את אהרן ובמחולות , “And Miriam the prophetess, the sister of Aharon, took her drum in her hand and all the women went forth after her with drums and with dancing." Since they danced then, they didn't dance with the egel. But the men didn't dance at kriyas Yam Suf, and they ended up dancing with the egel, as it states (32:19), ומחולות העגל את וירא, "And Moshe saw the egel and the dancing." So, we see the importance of being happy with kedushah and ruchniyos, and then we won't be tempted to seek happiness in the tumah.
The Levi'im also didn’t sin with the egel (see 32:26). This is because Levi'im serve Hashem with music and joy in the Beis HaMikdash, and where there's joy, one doesn’t fall into the trap of avodah zarah.
As we wrote, this week, when the egel is discussed, it is an opportune time to be strong and to keep away from atzvus. It is Adar, after all, and Chazal say, אדר משנכנס בשמחה מרבין , "When Adar arrives, we increase joy." בשמחה is gematriya שנה, year. The Ohev Yisrael teaches that the happiness of Adar brings joy to the entire year. בשמחה is also the letters of מחשבה. Because when one thinks positive thoughts, he will be happy.
