The Gemara (Sotah 49.) states: What keeps the world in existence? It is the דסדרא קדושא, the kedushah that we say in לציון ובא."
Kedushah is a very lofty tefillah. Sefer Heichalos (quoted in Tur, Orach Chaim 125) teaches, "When Bnei Yisrael say kedushah, Hakadosh Baruch Hu says, 'I don't have a pleasure in the world like that time when their eyes are raised to my eyes, and my eyes look into theirs."
Shulchan Aruch (1332:1) states, "You have to be very cautious to say it with kavanah," and the Zohar Hakadosh discusses great things regarding this tefillah.
Reb Asher of Stolin zy'a (Seder Hayom, written in Beis Aharon) says, "Be very cautious with לציון ובא (דסידרא קדושא) to say it with a lot of kavanah, because it is a tikun for the entire day, that everything should be מסודר, organized."
We say kedushah in the brachah אור יוצר before Kriyas Shma, again at Shemonah Esrei (ץ"הש חזרת) and a third time in לציון ובא. Actually, we say kedushah twice in ובא לציון because we say 'ה קדוש קדוש קדוש and ברוך ממקומו 'ה כבוד , and then we also repeat these verses in the Targum, in Aramaic.
הלקט שבלי (quoted in Beis Yosef, Orach Chaim 132) teaches the history of the establishment of kedushah in לציון ובא. "They established another kedushah to be said in לציון ובא. This was because there was a time that they couldn’t say kedushah in the tefillah because the goyim issued a decree that forbade them from saying kedushah, and spies were stationed in the beis knesses to ensure compliance. After the tefillah, the spies left, and then the community would say the kedushah and the targum (the translation in Aramaic) because of their love for it, so it would be like they said kedushah twice. Once corresponding to the kedushah of יוצר אור (in the brachos of kriyas Shma) and a second time corresponding to the kedushah that is said in ץ"הש חזרת of Shemonah Esrei. Although in our times, we say kedushah amid the tefillah, the custom to say kedushah in לציון ובא remains because they were concerned that perhaps the resha'im will reenact the gezeirah due to our sins (and once again, it might be forbidden to say kedushah in the tefillah)."
Let us repeat the הלקט שבלי's lesson in our own words. The goyim stood in the beis knesses to prevent people from saying kedushah. The community didn't lose hope; they weren't mevater on saying the kedushah. They said, "No! No! We refuse to give up! We won't be mevater on the kedushah!" With mesirus nefesh, as soon as the resha'im left the beis knesses, their hearts burst forth with a shout קדוש קדוש קדוש, and they said it twice to compensate for the two kedushos that they missed.
So, we can explain that the specialty of the tefillah לציון ובא is that it expresses the deep desire of the Jewish nation to serve Hashem and to be sanctified with Hashem's kedushah. The Jewish people didn't say, אונס פטריה רחמנא , it was an אונס, we have no choice." They sought opportunities and ways to say the kedushah with mesirus nefesh.
One of the חטא על's that we say on Yom Kippur is וברצון באונס לפניך שחטאנו חטא על, "For the sins that we committed before you by with an אנוס and willingly." The question is why we are asking for repentance for the aveiros that we committed באונס, which means the aveiros that were forced onto us. Those aveiros weren't our fault?!
The Chasam Sofer (Drashos 166) explains that the phrase should be read together, באונס וברצון , and we are asking for those aveiros that we committed by accident, באונס, and we were happy that we were able to transgress (ברצון). We are repenting that we had a רצון, desire and satisfaction, to be forced to sin באונס.
The kedushah we say in לציון ובא demonstrates that we aren't like the people who are happy to be exempt from performing a mitzvah. We seek and find ways to keep the Torah.
Story:
A Yid and a goy were traveling together and stopped on the side of the road to eat lunch. "Do you want some wine?" the goy asked. "No thanks. Jews aren't permitted to drink the wine of gentiles." "How about a sausage? I have extra." "No, thanks. We can't eat that either." "It is delicious. You’re sure you can't even taste it?" "I'm positive. A Jew is only permitted to eat such foods when his life is in danger." "What do you mean?" "Well, let's say someone is ill, and a doctor says he has to eat these foods to live." "Then you would be allowed to eat it?" "Definitely. Or let's say a goy takes out a knife and says, 'If you don't eat this food, I will kill you,' then we would also be allowed to eat it." Suddenly, the goy took out his knife and said menacingly, "Eat my food, or I'll kill you." The Yid, whose life was now in danger, began eating. What could he do? It was pikuach nefesh. A few minutes later, the goy said, "I'm sorry I did that to you. I was just joking. I wasn't going to kill you." The Yid put down the meat and pushed the wine aside, and said, "I forgive you for playing that prank on me, but I won’t forgive you for revealing it was a joke so soon. Couldn’t you wait until I finished the meal!?" But the proper approach should be that we don't want to perform aveiros ch”v, even when we are an אנוס.
