In Parshat Va’Etchanan, as B’nai Yisrael are about to enter the Land of Israel, Moshe tells them (Dvarim 4:39):
Viyadata hayom vihashevota el levavecha ki HaShem hu haElokim bashamayim mimaal v’al haaretz mitachat ein od.”
You will know today and take to your heart that God is the only God in heaven above and on earth below; there is no other.”
We are familiar with this quote as it was later adapted into the Aleinu prayer which we recite three times a day.
According to Rabbi Yisrael Yehoshua Trunk of Kutna who lived at the end of the 19th century, when we look at our daily lives we can see God’s Divine Providence and all of the hidden miracles that He performs. Seeing what God has done for us, we must internalize in our hearts that He is our God. The reason that it says “today” is because each day, when we see God’s miracles we recognize that our God is the only true God.
Aleinu affirms our belief in one God. In the Middle Ages, many Jewish martyrs who were burned at the stake recited Aleinu as they were being executed in the hope that one day all of the nations would recognize God.
There is a line in Aleinu which the Church thought was an affront to Christianity: “For they bow to vanity and emptiness and pray to a God which helps not.” This quote is from Yishayahu 45:20 and was actually part of the prayer before Christianity even existed. From the year 1400, siddurim in parts of Europe were censored and those words were removed. In 1703 in Germany the Jews were forced to sing Aleinu out loud so that the authorities could make sure that the Jews weren’t quietly saying those words. Today, many siddurim have put those words back, yet some siddurim (such as the Artscroll) still have those words in parenthesis.
Outside of Israel, every synagogue that I have been to on Shabbat recited Aleinu out loud omitting the controversial words, yet in Israel the full Aleinu is almost always said quietly. Originally, I thought that it was because in Israel by the end of the service people want to get home to eat and rest as Shabbat is our only day off while in Chutz Laaretz (outside of Israel), people have time to sing — they still have a whole other day off on Sunday. I am now more convinced that in Israel the prayer is said quietly because in Israel there was no edict to force the congregation to sing it out loud. Rabbi Yosachar Yaakovson (1901-1972) heard that in Amsterdam in the late 1940s the first part of Aleinu was being sung out loud even though they never had a decree in Holland to sing it out loud. He believes that the minhag spread to more countries even though it was not forced upon them like in Germany.
It is time for Jews around the world to recite the full Aleinu as we wish and strengthen our belief in one God.