The care with which we bury the dead expresses our faith in the victory over everlasting death which Our Lord Jesus Christ has won in our human nature by His own Death and Resurrection. We bury the dead in the sure hope of the resurrection of the body, when their mortal bodies will share fully in the glory of the Risen Christ."In the middle of the 11th century, St. Odilo, the abbot of Cluny (France), said that all Cluniac monasteries were to offer special prayers and sing the Office for the Dead on November 2, the day after the feast of All Saints. The custom spread from Cluny and was was adopted throughout the entire Roman Catholic Church. Now the entire Church celebrates November 2nd as All Soul's Day.
Yet this does not mean that the bodies of the departed are to be despised and flung aside, and above all those of just and faithful men, whose bodies have been used by their spirits as instruments and tools for doing all their good works. For just as the greater the affection one has for his parents, the more treasured are the father’s clothing and ring and all such things to those who survive him, in the same way the bodies themselves should not be neglected, since we wear them and are joined to them more closely than anything which we ourselves put on. For our bodies are not some ornament or aid which is added from outside, but belongs to the very nature of man.
Funerals with dutiful piety
So also in ancient times the funerals of just men were arranged with dutiful piety, and their funerals were celebrated, and burials provided for, and while they were still alive they gave instructions to their sons about their burial or even about moving their bodies to another place.
Tobias also was commended by the testimony of an angel for burying the dead, thus obtaining favor with God (Tobit 2:9). The Lord Himself also, when He was about to rise on the third day, both proclaimed, and commended for preaching the good work of the pious woman who poured a precious perfume over His limbs and did it for his burial. And the Gospel commemorated with praise those who took Christ’s body from the cross and carefully and with reverent honor saw it wrapped and laid in the tomb.
However these authorities in no way suggest that dead bodies can experience any feeling; but rather, they signify that the providence of God (Who is pleased with such acts of piety) is concerned also with the bodies of the dead, in order that our faith in the resurrection might be strengthened. From these we can also profitably learn that the reward for giving alms to those who are alive and have their senses must be great, if God does not overlook even those things which with duty and diligence we do for the lifeless bodies of men...
Mark of good and human disposition
If this be true, then also providing a burial place for bodies at the memorials of saints is a mark of a good and human disposition towards the remains of one’s friends. For if there is a sanctity in providing burial, there must also be sanctity in paying attention to where the burial occurs. But while it is desirable that there be such solace for the survivors, by which means they can show their pious attitudes towards their beloved, I do not see what assistance this can be to the dead except in this way: that when remembering the place in which the bodies of those whom they love have been laid, they might with their prayers commend the departed to those same saints as if they were patrons undertaking to aid them before the Lord. Indeed they would still be able to do so, even if they were not able to be interred in such places...
Supplications for all the departed
But even if, due to the lack of opportunity, some necessity does not permit bodies to be interred, or to be interred in such places, one should still not neglect prayers for the souls of the dead. For in its general prayer the Church undertakes to make such supplications for all the departed in our Christian and Catholic fellowship, even without mentioning their names. Thus those who do not have parents or sons or any relatives or friends still have the one pious mother common to all Christians to perform these acts for them. But no matter how holy the places where lifeless bodies are laid, I think their souls will not profit in the least without such prayers for the dead and if they are not made with the right faith and piety.
Spirit of the departed aided
When therefore a Christian mother desired to have the body of her dead Christian son deposited in the basilica of a martyr because she believed that his soul would be aided by the merits of the martyr, the very believing of this was a type of supplication, and this would profit if anything would. And in that her thoughts return to this same tomb, and in her prayers she more and more prays for her son, the spirit of the departed is aided, not by where its dead body has been placed, but by the living affection of the mother which remembers that place. For at once the thought of who is being commended and to whom, does affect the pious mind of the one praying in a way that is not unprofitable.
Use the body in a way fitting to prayer
For also when men pray to God they use their bodies in a way that is fitting to prayer. So when they kneel, stretch out their hands, or even prostrate themselves on the ground, or whatever other visible actions they perform, they do this as if God will then know the invisible desire and intention of their heart, even though He does not need such actions to know what is in the human mind. Yet in so doing, a person rouses himself to pray and groan even more humbly and more fervently. I do not understand how it is that although these bodily motions cannot be made unless a mental activity comes first, yet when these are done in an outward and visible way, that inward invisible activity which caused them also increases.
The heart's affection grows
And so the heart’s affection which first caused them to be done itself grows because they are done. Yet truly if any man is held back, or even bound, so that he cannot do these actions with his limbs, one cannot conclude that his inner man is not praying, or that it has not in its most secret chamber thrown itself upon the ground in remorse before the eyes of God.
In the same way it does make a great difference where a person places the body of a departed one for whose spirit he prays to God, because both beforehand the affection chose a spot which was holy, and later, after the body is laid there, the mind’s recollection of that holy spot renews and increases the affection which came first; yet, even if he is unable to bury his beloved in the place which his pious mind desires, he should still in no way stop the required prayers and commending of that person.
For wherever the body of the departed may or may not lie, the spirit requires rest. For when the spirit leaves the body, along with it goes consciousness, by which one is able to ascertain the state one is in, whether good or bad. Nor does it look for assistance for its life from that flesh to which it did itself give life and then withdrew life when it departed, and will again give it back when it returns. For the spirit adds merit to the flesh (not vice versa) even in its resurrection, whether it comes alive for punishment or for glory.
Source: The above is taken from the website of the SSPX