Each morning, immediately after Baruch She'amar, we recite the 100 th chapter of Tehillim – Mizmor Le'toda, the Psalm that was sung during the offering of the Korban Toda (thanksgiving sacrifice) in the Bet Ha'mikdash. Several explanations have been given for why this chapter was incorporated into our daily prayer service. One reason is that we recite this chapter to express gratitude for the creation of light which we enjoy anew each morning. The Kab Ha'yashar (Rav Tzvi Hersh Kaidanover, d. 1712) explains that we thank Hashem for the daily miracles He performs for us without us even knowing. We are all aware of many things that Hashem does to help and protect us, but there are also countless occasions when we are helped in ways we know nothing about. We'll never know about the germs in the air that we do not inhale, or the looming threats that were neutralized before affecting us. We therefore recite Mizmor Le'toda each morning to acknowledge that our debt of gratitude to the Almighty is far greater than what we can imagine. Another reason is that this chapter contains the famous verse, "Ibdu Et Hashem Be'simha," urging us to serve Hashem joyfully. This chapter is meant to put us in a state of genuine Simha (joy) as we begin to recite Pesukeh De'zimra. What's important is not just what we say, but how we say it. If we speak Hashem's praises feeling unhappy, then we are not properly fulfilling our obligation. And so we recite "Ibdu Et Hashem Be'simha" right at the outset of Pesukeh De'zimra to put ourselves in the proper frame of mind for this section of praise. Yet another reason for reciting Mizmor Le'toda is that this recitation serves as our own Korban Toda. In the times of the Bet Ha'mikdash, a person would bring this sacrifice after being saved from a perilous situation – specifically, after being rescued from captivity, after recovering from a serious illness, after a sea voyage, or after traversing a desert. We all experience these situations in various forms, and thus in the absence of the Bet Ha'mikdash, when we are unable to offer this sacrifice, we instead recite Mizmor Le'toda, the chapter which was sung during this offering. For this reason, some Kabbalists maintained that one should stand while reciting Mizmor Le'toda, just as one would stand during the offering of his sacrifice. We, however, follow the practice taught by the Arizal to recite Mizmor Le'toda sitting. We are not actually reenacting the offering of the Korban Toda – as evidenced by the fact that we recite it even on days when this sacrifice could not be brought, such as on Pesach (since this sacrifice included leavened bread). This recitation merely commemorates the sacrifice, and so we do not need to stand. The Shulhan Aruch writes that Mizmor Le'toda should be sung in a pleasant melody. This is not commonly done, and Rav Yosef Shalom Elyashiv (Jerusalem, 1910-2012) is said to have left unanswered the question of why this is the case. Others suggested different theories to justify the widespread practice not to sing this chapter. Rav Haim Kanievsky (1928-2022) said that the Shulhan Aruch perhaps meant not that this chapter should actually be sung, but rather that it should be recited slowly. Others explain that it should be recited with joy, but not necessarily in a melody. The Hesed La'alafim (Rav Eliezer Papo, 1785-1828) writes that we do not know the correct tune to sing, and so we recite this chapter instead of singing it. These reasons were suggested in defense of the custom not to sing Mizmor Le'toda, but it seems clear that if one can, it is preferable to sing this chapter. Rashi, commenting to the opening verse of Parashat Hayeh-Sara, tells us that "Bat Kuf Ke'bat Chaf" – Sara at the age of 100 was no different from the way she was at age 20. Some have explained this remark as an allusion to two very different chapters of Tehillim that we include in our morning prayer service: Mizmor Le'toda – the 100 th chapter, and La'menase'ah Mizmor Le'David Ya'ancha Hashem – the 20 th chapter. Mizmor Le'toda, as discussed, is a song of thanksgiving, whereas La'menase'ah is a desperate plea for help during times of distress. Rashi's comment alludes to us that Sara Imenu treated "chapter 100" no different than "chapter 20" – meaning, she thanked Hashem for all the goodness He bestowed upon her no less than she begged for help during times of hardship. As important as it is to always turn to Hashem for His assistance and to fill our needs, it is no less important to say "Mizmor Le'toda," to thank Him from the bottom of our hearts for His kindness toward us and all the wonderful blessings in our lives.