The first thoughts that often come to mind at the mention of "kaddish" are those in association with death and mourning. Contrary to this common misconception, the kaddish is not related whatsoever to death, the deceased, or the afterlife. There is not even a single mention of death in the kaddish. In fact, the original function of kaddish was as a communal praise of God to be recited at the conclusion of a public Torah study session. The kaddish was actually created in response and is intended to recall the destruction of the Beit Hamikdash and the exile of the Jewish people. One should endeavor to hear at least seven kaddishes each day, with some authorities requiring that one hear a minimum of twelve kaddishes each day.
Inspired by the prophet Yechezkel's vision of God, the kaddish is the classical and eternal formula for sublime praise of God. It was composed by the Men of the Great Assembly shortly after the destruction of the first Beit Hamikdash. The original version of the kaddish only went until the words "d'amiran b'alma", with the remaining insertions having been added at later times. Talking while kaddish is being recited is considered to be an exceptionally severe offense.
The kaddish was written in Aramaic in order that everyone would be able to understand its powerful meaning and content, as Aramaic was the vernacular language of Babylonian Jewry. It was also written in Aramaic as it is a language that the angels don’t understand with the exception of Michael, Gavriel, and Raphael. There was concern that if the angels were aware of the powers of kaddish that they would attempt to plagiarize it. Some suggest that the kaddish was arranged and recited in the unfamiliar Aramaic as a response to a governmental decree which forbade Jews from reciting it. It is interesting to note that there are several words in the Torah written in Aramaic. According to some authorities, Aramaic is simply a tattered form of Hebrew.
Not only does the recitation of kaddish have the ability to reach the highest levels of Heaven, but even one who merely responds to the kaddish with the proper intentions, particularly the central "yehay shmay rabba" response, can annul any evil decrees which may have been decreed against oneself. We are taught that the entire world is sustained in the merit of the "yehay shmay rabba" response. So too, we are taught that God gets excited when He hears His children praise Him with "yehay shmay rabba". We are also taught that anyone who is careful to answer "amen" to kaddish in this world will merit to respond "amen" in the next world. It is interesting to note that the phrase "ve'yishtabach v'yitpaar v'yitromam v'yitnasei v'yithadar v'yitaleh v'yithalal" consists of seven words, each of which begins with the letter "vav," which has the numerical value of six. These seven words multiplied by six equal forty-two, alluding to the forty two letter name of God. Additionally, each of these seven words consists of six Hebrew letters, again alluding to the forty two letter name.
Today there are five versions of the kaddish each of which is recited at its specifically designated occasion, as follows:
- The Half-Kaddish – recited in order to distinguish between the different segments of the prayer service
- The Mourner's Kaddish – recited by mourners at the end of prayers as well as those observing a yartzeit
- The Full Kaddish – recited by the leader at the conclusion of the service
- The Kaddish of the Rabbis – recited after Torah study
- The Kaddish following burial – recited after burial. Oddly enough, it is also recited when concluding the study of entire tractate of Talmud.
It wasn't until the 13th century that the kaddish became a prayer which was delegated to mourners and those observing a yartzeit. This is related to the principle that the performance of good deeds, especially those things which allow others a share in the mitzva, bestows merits to one's departed ancestors. Offering the congregation the opportunity to praise God through their response to kaddish is considered one such opportunity. One who does not recite the kaddish for his parents is in contempt of the mitzva to honor one's mother and father. Those who for whatever reason cannot recite kaddish on behalf of their deceased parents should hire someone else to do so. One is permitted to recite the kaddish on behalf of a number of different people at once.
The kaddish is recited by those mourning for a parent for eleven months. During this period it is believed that the souls of the departed undergo a difficult cleansing period in preparation for their share in Heaven. Truth be told, this cleansing process can often extend to twelve months for those who were particularly rotten during their lifetime. Nevertheless, in order not to arouse any suspicions on the deceased's character, common custom is to recite the kaddish for only eleven months on the assumption that the deceased was of worthy character. With its many more 'amen' opportunities, leading the prayer service is considered to be of even greater benefit to the dead than the recitation of kaddish. Indeed, kaddish was only delegated to the mourners because in times gone by most of the populace was uneducated and incapable of leading the service.
Historically the mourners would recite the kaddish individually, not together in unison as is done today. One should never enter into an argument over who is to lead the services or recite the kaddish. In fact, the kindness of deferring and allowing others to recite the kaddish or lead the services will do more on behalf of one's departed than having recited the prayer itself.
It is considered meritorious to recite kaddish for one's grandparent if there is no one else who is able to do so. However, one should never recite the mourner's kaddish, for whatever reason, while one's parents are still alive unless explicit permission has been given. Every prayer service should include a kaddish after aleinu regardless whether or not there is a mourner present. Some suggest that those who recite the mourner's kaddish should wear a tallit even if they do not ordinarily do so (i.e. one who is not married).
There's an eerie tale which illustrates some of the redeeming powers that kaddish is reputed to have. Once Rabbi Akiva was walking in a cemetery and met a very strange and dirty person clearly exhausted from schlepping wood. Rabbi Akiva approached this fellow and inquired who he was and what his occupation was. The man replied that he is dead, but in life he worked as a tax collector who favored the rich and tormented the poor. As a punishment for his deeds he is required to fetch wood each day in order to light the fires of Hell in which he is then burned.
Rabbi Akiva asked this fellow if he had been told how he may relieve his awful suffering. The man responded that he had heard that if his son would say kaddish in the synagogue then he would be released from Hell in its merit. Rabbi Akiva then sought out this man's son and taught him how to say the kaddish. The man later returned to Rabbi Akiva in a dream to thank him and reported that indeed, he had been released from his punishment.
We are taught that in the future God will sit in Heaven and teach Torah to the righteous. Following this study Zerubavel will stand and recite the kaddish which will be heard from one end of the world to the other. All mankind will respond to this kaddish including the souls of those who are deceased and even those that are in Hell. Immediately thereafter, the forty thousand gates of Hell will open to release all those who were condemned to Hell, into Paradise.
 Aruch Hashulchan 55:5, Tosfot Berachot 3a
 Aruch Hashulchan 55:1
 Yechezkel 38:23
 Aruch Hashulchan 55:1, Shulchan Aruch Harav 56:1
 Aruch Hashulchan 55:8
 Mishna Berura 56:1
 Aruch Hashulchan 55:1, Tosfot Berachot 3a
 Elya Rabba 56:5
 Tosfot Berachot 4a
 Elya Rabba 56:5
 Bereishit 31:47
 Shu"t Harama 126
 Inspired by Daniel 2:20
 Shabbat 119b
 Sota 49a
 Berachot 3a
 Sefer Chassidim 883
 Kaf Hachaim 55:1-4
 This kaddish is unique because it is unusually long and contains some tooth-breaking Aramaic. Why is this kaddish so different from all other kaddish texts and why do we say it on these two occasions? Rabbi Yaakov Kaminetsky in his Emet L'yaakov on Y.D. 246:10 n. 130 explains: The kaddish we recite at a siyum and at a burial do not have anything more than the usual kaddish. However, since there are so many ignorant people at both a siyum and burial, they translated and explained the text of the kaddish [in Aramaic] so that they will also understand it. See at: http://hirhurim.blogspot.com/2008/11/special-kaddish.html
 Some Sefardim have the custom to recite the kaddish for the entire week in which a yartzeit falls, not merely on the yartzeit day. Kaf Hachaim 55:23
 Sanhedrin 104a
 Y.D. 240:9
 Kaf Hachaim 55:30, Pele Yoetz "amen". See also Chazon Nachum (Weidenfeld) O.C. 117
 Torah Lishma 412, Dovev Meisharim 2:15
 Mishna Eduyot 2:10, Rema Y.D. 376:4
 Rema Y.D. 376:4, Kaf Hachaim 55:24, Rivevot Ephraim 8:353
 Pele Yoetz "amen"
 Y.D. 376:4
 Pele Yoetz "amen"
 Kaf Hachaim O.C. 53:96
 Rema Y.D. 240:24, Knesset Yechezkel 240, Shraga Hameir 5:52:6
 Rema O.C. 132:2, Pitchei Teshuva Y.D. 376:4, Kaf Hachaim 55:27-28
 Rema O.C. 132:2
 Elya Rabba O.C. 18:2
 Cited with slight variations in Machzor Vitri and Tanchuma Noach
 Otiot D'rabbi Akiva 7