Children recite Kaddish after the death of a father or mother. Reciting Kaddish not only saves the soul of the deceased from being sent to Gehenna; it also allows one’s parents to enter the Garden of Eden and elevates them from one level to the next.

I believe that I heard from my teacher of blessed memory [the Arizal] that it is good to recite this [the orphan’s] Kaddish for the death of one’s father or mother for the entire year, even on Shabbatot and festivals, since the reason [for the recitation of Kaddish] is not what many of the people think, that it functions only to save the soul of the deceased from being sentenced to Gehenna [and on Shabbat one is not punished with Gehenna]. Rather, there is an additional benefit, which is that it brings the soul into the Garden of Eden and elevates it from level to level. (Rabbi Hayyim Vital, Sha’ar HaKavanot, Derush HaKaddish)

Further reading: For more on the recitation of Kaddish, see A Concise Guide to Halakha, p. 504.

There is a Torah commandment to mourn one’s dead, and this is entirely a service of God. (Rabbeinu Baĥya ibn Ĥalawa, Kad HaKemaĥ, Evel)

When a child says Kaddish for his father or mother, it is as though he has sent them his greetings. When he learns a chapter of Mishna for their sakes, it is as though he has sent them a letter. When he does mitzvot and performs good deeds for the good of their souls, it is as though he has sent them an entire parcel. (Rabbi Aharon of Karlin)

Death is nothing; it is merely like walking from one room to another and opting for the more beautiful one. (Rabbi Menaĥem Mendel of Kotzk)

The Torah commandment to mourn serves to emphasize the loss of the treasure of life, which allows one to continue to ascend without limit. For this tremendous purpose, the Holy One, blessed be He, brings [a person] into the world. The living person should take heed and occupy himself with the purpose of his birth. (Rabbi Yeĥiel Mikhel Tukachinsky, Gesher HaĤayyim 3:1)

Further reading: For the Yizkor prayer, which is recited on festivals for the elevation of the souls of deceased relatives, see A Concise Guide to Halakha, p. 171.