7 For the apostle, in speaking of the love which husbands ought to have for their wives gives, as an example, the love of the soul for the body. The words are: "He that loves his wife, loves himself: for no man ever yet hated his own flesh, but nourishes and cherishes it, even as Christ the Church." Look at the whole animal creation, and you find in the instinctive self-preservation of every animal this natural principle of love to its own flesh. It is so not only with men, who, when they live aright, both provide for the safety of their flesh, and keep their carnal appetites in subjection to the use of reason; the brutes also avoid pain, and shrink from death, and escape as rapidly as they can from whatever might break up the construction of their bodies, or dissolve the connection of spirit and flesh; for the brutes, too, nourish and cherish their own flesh.
"For no one ever yet," says the apostle, "hated his own flesh, but nourishes and cherishes it, even as Christ the Church." See where the apostle begins, and to what he ascends. Consider, if you can, the greatness which creation derives from its Creator, embracing as it does the whole extent from the host of heaven down to flesh and blood, with the beauty of manifold form, and the order of successive gradations.
Source: Reply to Faustus the Manichaean (New Advent)