3 Therefore, O fool, be instructed by this, that each of the seeds is clothed in its own body. Never do you sow wheat and yet reap barley, and never do you plant a vine and yet it produced figs; but everything grows according to its nature. Thus also the body that was laid in the earth is that which shall rise again. And as to this, that the body is corrupted and wastes away, you ought to be instructed by the parable of the seed; that as the seed, when it is cast into the earth, decays and is corrupted, and from its decay it produces and buds and bears fruit.
For the land that is ploughed, into which seed is not cast, produces not fruit, even if that land drinks in all the rain. So the grave in which the dead are not buried, from it men shall not issue forth in the quickening of the dead, though the full voice of the trumpet should sound within it. And if, as they say, the spirit of the just shall ascend into heaven and put on a heavenly body, they are in heaven. And He Who raises the dead dwells in heaven. Then when our Saviour shall come, whom shall He raise up from the earth?
And why did He write for us:— The hour shall come, and now is, that the dead also shall hear the voice of the Son of Man, and they shall live and come forth from their tombs? For the heavenly body will not come and enter into the tomb, and again go forth from it.
Source: Demonstrations (New Advent)