Tertullian on the union of body and soul and parenthetically on baptism and the Eucharist.
The flesh, then, is washed, so that the soul may be made clean. The flesh is anointed, so that the soul may be dedicated to holiness. The flesh is signed, so that the soul too may be fortified. The flesh is shaded with the imposition of hands, so that the soul too may be illuminated by the Spirit. The flesh feeds on the Body and Blood of Christ, so that the soul too may fatten on God. They cannot, then, be separated in their reward, when they are united in their works.
Tertullian's The Resurrection of the Dead [8,2] A.D. 208-212.