Why the Church of God performs the commemoration of souls?

“Giver rest, O Christ, among the Saints to the souls of Your servants, where there is no pain, no sorrow, no grieving, but life everlasting.”

Since it often happens that certain people suffer death prematurely, in a foreign land, at sea, on trackless mountains, on precipices, at chasms, in famines, wars, conflagrations, and cold perhaps, being poor and without resources, they have not been vouchsafed the customary psalter readings and memorial services, moved by love for mankind, the Divine Fathers ordained that the Orthodox Catholic Church make commemoration of all people, a tradition which they inherited from the Holy Apostles, in order that those who, dues to some particular circumstance, did not receive the customary obsequies individually, might be included in the present general commemoration, indicating that whatever is done on their behalf confers great benefit on them.

This is one reason why the Church of God performs the commemoration of souls. A second reason is that, since the Holy Fathers intended, as is fitting, to assign the observance of the Second Coming of Christ to the following day, they appointed a commemoration of all souls on this day, as if propitiating the dread and unerring Judge to show them His innate compassion and place them in the promised Paradise of delight. A third reason is that, since they intended to expound the banishment of Adam on the following Sunday, they devised the present commemoration, on this day of rest, as a respite from, and end of all human affairs, so that they might start from the beginning, that is, the banishment of Adam–for the final event that we will experience is the examination by the impartial Judge of all the deeds that we have committed in our life–and so that, putting fear into men thereby, they might make them ready for the contest of the Fast.

We always commemorate souls on Saturday, because savvaton (Sabbath) means “rest” in Hebrew; and since the dead have rested from worldly and all their cares, we offer supplications for them also on the day which means “rest’. It has become customary for us to do this every Saturday. On the present Saturday, we observe a universal commemoration, beseeching God for all the pious. The Holy Fathers, knowing well that what is done on behalf of the reposed, that is, memorial services, almsgiving, and liturgies, affords them great respite and benefit, allow the Church to do so on both an individual and a general basis, a tradition which they received from the Holy Apostles, as Saint Dionysios the Areopagite tell us. (To be continued)

“Through the Apostolic Constitution (Book VIII, ch. 42), the Church of Christ has received the custom to make commemorations for the departed on the third, ninth, and fortieth days after their repose. Since many throughout the ages, because of an untimely death in a faraway place, or other adverse circumstances, have died without being deemed worthy of the appointed memorial services, the divine Fathers, being so moved in their love for man, have decreed that a common memorial be made this day for all pious Orthodox Christians…”

(Source: http://o-nekros.blogspot.com/2018/02/why-church-of-god-performs.html)