The sacramental understanding of the historic Church is predicated on, as is all Christian dogma and experience, the Incarnation. Matter matters because the God of matter became matter for our sake. This understanding extends to the human body. Christianity rejects the dualism of Plato, the Gnostics, the Manicheans, and Descartes that would in any way destroy the unity of the human body and human soul/spirit. (I here make no argument as to whether and in what way the human soul and human spirit are two separate things as 1 Thessalonians 5:23 seems to explicitly indicate.) The human body cannot be reduced to mere matter because a human person is the unity of body and soul/spirit. In fact, the Christian is indwelt by the Holy Spirit in both body and soul/spirit. The reality of the indwelling of the Holy Spirit in the body of the believer is evidenced by the numerous instances of the incorruption of the bodies of saints. And it is on this reality that is based the historic Christian prohibition against cremation.
The biblical case looks something like this. First, note that the body is referred to as the temple of the Spirit.
Know ye not that ye are God's temple, and that the Spirit of God dwelleth in you? If anyone corrupt the temple of God, God shall bring this same one to corruption, for the temple of God is holy, which ye are. (1 Corinthians 3:16-17)Or know ye not that your body is a temple of the Holy Spirit Who is in you, Whom ye have from God, and ye are not your own? For ye were bought with a price; glorify then God in your body and in your spirit, which are God's. (1 Corinthians 6:19-20)
That this is not merely a figurative manner of speaking about the relationship between the Christian body and the Holy Spirit is evidenced by 1 Corinthians 6 in which the prohibition against having sex with a prostitute is predicated precisely on the fact that the Holy Spirit really and metaphysica