|In the times of the Bet Hamikdash, there existed a Thanksgiving offering which, in the words of Rashi (Vayikra 7:12), people would offer in gratitude of a personal mirage, and was known as Korban Toda. In the absence of the Bet Hamikdash, our Sages instituted as a substitute the recitation of Mizmor 100 (Mizmor Letoda) during Pesuke Dezimra. Since the laws of this offering stipulated that it was not brought on Shabbat or Yom Tov, the Rama (O.H. 51:9) says in the name of the Tur (O.H. 51), that this Mizmor is also not recited on these days. Furthermore, the offering was brought together with leavened bread, and therefore, this Mizmor is also not recited on the eve of Pesah, when Hametz is already forbidden. Finally, the Korban Toda was not offered on the eve of Yom Kippur since it would not be able to be consumed that night, when the fast had already begun, and thus, the Rama continues, Mizmor 100 is also not recited on that day.The Bet Yosef (O.H. 281) questions the logic of the aforementioned Tur by saying that the Mizmor is simply an expression of gratitude and does not necessarily need to parallel the laws of the actual Korban Toda. Indeed, Rabbi Baruch Toledano (Kitzur Shulhan Aruch, pg. 44) writes that the Moroccan custom was to refrain from reciting this psalm on the days listed above, and this is echoed in the Siddur Bet Oved. Rabbi Elazar Tobo (Pekudat Elazar), who emigrated to Israel from Morocco, writes that this was also the custom among the Sephardic community in Jerusalem, which included an established Moroccan communityThe Siddur Bet Oved cites an opinion from Rabbi Israel Saruk (Mahari Saruk), who says that since the Korban Toda was offered standing up, so too, Mizmor Letoda should be recited standing up. Nevertheless, the HIDA says that although it commemorates the Korban Toda, the Mizmor is not literally like the offering and therefore it may be recited sitting down, and this appears to be the common custom. Summary: The Moroccan custom is for Mizmor Letoda to be skipped on Shabbat, Yom Tov, Erev Pesah and Erev Yom Kippur. The original custom was for it to be skipped on Tisha Be’Av as well. Mizmor Letoda is recited sitting down.