22 Which things being so, let us not think that to the dead for whom we have a care, any thing reaches save what by sacrifices either of the altar, or of prayers, or of alms, we solemnly supplicate: although not to all for whom they are done be they profitable, but to them only by whom while they live it is obtained that they should be profitable. But forasmuch as we discern not who these be, it is meet to do them for all regenerate persons, that none of them may be passed by to whom these benefits may and ought to reach.
For better it is that these things shall be superfluously done to them whom they neither hinder nor help, than lacking to them whom they help. More diligently however does each man these things for his own near and dear friends, in order that they may be likewise done unto him by his. But as for the burying of the body, whatever is bestowed on that, is no aid of salvation, but an office of humanity, according to that affection by which “no man ever hates his own flesh.” Whence it is fitting that he take what care he is able for the flesh of his neighbor, when he is gone that bare it.
And if they do these things who believe not the resurrection of the flesh, how much more are they beholden to do the same who do believe; that so, an office of this kind bestowed upon a body, dead but yet to rise again and to remain to eternity, may also be in some sort a testimony of the same faith? But, that a person is buried at the memorials of the Martyrs, this, I think, so far profits the departed, that while commending him also to the Martyrs' patronage, the affection of supplication on his behalf is increased.
Source: On Care to be Had For the Dead (New Advent)