The covenant theology of human sexuality is nearly identical to the papal theology of the body when the latter is applied to the marriage act. The Pope has given us at least two statements that are not formal parts of the overall theology of the body but which apply it to the marriage act. The longer statement is in Familiaris Consortio, his 1981 Apostolic Exhortation on the Family.
In its most profound reality, love is essentially a gift; and conjugal love, while leading the spouses to reciprocal “knowledge” which makes them “one flesh” does not end with the couple, because it makes them capable of the greatest possible gift, the gift by which they become cooperators with God for giving life to a new person. Thus the couple, while giving themselves to one another, give not just themselves but also the reality of children, who are a living reflection of their love, a permanent sign of conjugal unity and a living and inseparable synthesis of their being a father and a mother.
He wrote a shorter statement in 1994, ten years after he finished the lectures that constitute the “theology of the body.” In his Letter to Families from Pope John Paul II, he said this about the marriage act: In the conjugal act, husband and wife are called to confirm in a responsible way the mutual gift of self which they have made to each other in the marriage covenant.
For comparison, here once again is the basic statement of the covenant theology of sexuality: Sexual intercourse is intended by God to be at least implicitly a renewal of the marriage covenant.
In both statements, the key is that the marriage act really ought to be a true marriage act. That is, it ought to confirm and renew the commitment, the fidelity, the love, the gift of self that they pledged in their marriage covenant. Both statements focus on what the spouses have done. It is they who have entered into the lifelong covenant of marriage.
John F. Kippley
Sex and the Marriage Covenant