The Mishna (Megillah 2:4) in today’s daf (Megillah 20a) lists a variety of mitzvot that need to be performed in the daytime and which are invalid if performed before daybreak – namely: 1) The (daytime) reading of the Megillah, 2) Brit Milah (Circumcision), 3) Tevillah (Immersion in a Mikveh) for those who have been in contact with impurity, 4) Sprinkling of the ashes of the Parah Adumah (Red Heifer) for someone who has been in contact with the dead, 5) Tevillah (Immersion in a Mikveh) of a woman ‘Zavah Ketana’ who is referred to as being a ‘Shomeret Yom K’Neged Yom’ (someone who watches a day corresponding to a day).
Clearly this list is meant to be of halachic (legal) significance in which it informs us about ‘when’ certain mitzvot may or may not be performed. However, what also seems clear is that a profound hashkafic (outlook) lesson is also being taught in this Mishna. This is because 4 of the 5 mitzvot listed are actions that directly affect both body and soul, with most of them involving some form of immersive physical action which is accompanied by a transformative spiritual outcome.
With this understood, we can now appreciate what I believe is being taught in our Mishna – that Megillat Esther needs to be not just a story which is intellectually and emotionally engaging when heard with our ears, but instead, a mitzvah that involves as much of our body as possible (nb. for a further story which speaks of the importance of involving as much of our body as possible in performing a mitzvah, see Eruvin 53b-54a where Beruria quotes Shmuel II 23:5 to teach that Torah study should involve as many of our limbs as possible); one that should be an immersive experience in whichever way possible, and one that should be accompanied by some form of transformative spiritual outcome in our life.