The Gem. brings different proofs that the Megilah has to be read in proper order.
Rabbah's reason is from the Posuk Mimizrach Shemesh ad Mevoyoy . Isn't it strange that Rashi changes the order of the Posuk when we're explicitly talking about not changing the order of things?!
Kol Tuv
alex lebovits, toronto,canada
One might read the Gemara as saying that we learn from this verse to recite Hallel in order as follows: just as the sun goes in order, from East to West, so too must Hallel be recited in its correct order.
Rashi does not accept this interpretation. What makes East to West the more "correct order?" All we see is that it starts at one point and ends at another.
Rather, Rashi (and Rabeinu Chananel) explains that we learn from the verse that just as the sun can never rise in the West or set in the East, but it only goes in one direction, so too Hallel can only be said in one order.
Had Rashi mentioned sunrise before sunset, we would have missed his point thinking that he is emphasizing the "correctness" and orderliness of the sun's path.
Be well,
Mordecai Kornfeld
Kollel Iyun Hadaf