Objection 1. It would seem that a man ought not to love his body out of charity. For we do not love one with whom we are unwilling to associate.
But those who have charity shun the society of the body, according to Romans 7:24: "Who shall deliver me from the body of this death?" and Philippians 1:23: "Having a desire to be dissolved and to be with Christ." Therefore our bodies are not to be loved out of charity.
Objection 2. Further, the friendship of charity is based on fellowship in the enjoyment of God. But the body can have no share in that enjoyment. Therefore the body is not to be loved out of charity.
Objection 3. Further, since charity is a kind of friendship it is towards those who are capable of loving in return. But our body cannot love us out of charity. Therefore it should not be loved out of charity.
On the contrary, Augustine says (De Doctr. Christ. i, 23,26) that there are four things that we should love out of charity, and among them he reckons our own body.
I answer that, Our bodies can be considered in two ways: first, in respect of their nature, secondly, in respect of the corruption of sin and its punishment.
Now the nature of our body was created, not by an evil principle, as the Manicheans pretend, but by God. Hence we can use it for God's service, according to Romans 6:13: "Present... your members as instruments of justice unto God." Consequently, out of the love of charity with which we love God, we ought to love our bodies also, but we ought not to love the evil effects of sin and the corruption of punishment; we ought rather, by the desire of charity, to long for the removal of such things.
Reply to Objection 1. The Apostle did not shrink from the society of his body, as regards the nature of the body, in fact in this respect he was loth to be deprived thereof, according to 2 Corinthians 5:4: "We would not be unclothed, but clothed over." He did, however, wish to escape from the taint of concupiscence, which remains in the body, and from the corruption of the body which weighs down the soul, so as to hinder it from seeing God. Hence he says expressly: "From the body of this death."
Reply to Objection 2. Although our bodies are unable to enjoy God by knowing and loving Him, yet by the works which we do through the body, we are able to attain to the perfect knowledge of God. Hence from the enjoyment in the soul there overflows a certain happiness into the body, viz., "the flush of health and incorruption," as Augustine states (Ep. ad Dioscor. cxviii). Hence, since the body has, in a fashion, a share of happiness, it can be loved with the love of charity.
Reply to Objection 3. Mutual love is found in the friendship which is for another, but not in that which a man has for himself, either in respect of his soul, or in respect of his body.
Source: Summa Theologica (New Advent)