The Christian’s body is designed for union with Christ and thus, belongs to Him (CRC Report 2019 p. 28). All other relationships a Christian has through his or her body are subjected to the lordship of Christ (CRC Report 29 p. 471). Christians are called to reflect Christ and His love for the Church in their sexual expression (Eph. 5:25-33). Because of these two truths, that the Christian’s body is united to Christ and the Christian’s use of the body reflects Christ’s relationship with the Church, Christianity stands against adultery and sex outside marriage.
Contrary to popular opinion, Christianity is not “anti-sex”. St. Paul’s letter to the Corinthians urges married couples to have sex as part of their commitments to one another (1 Cor. 7; Hays 47-52). However, the Church has limited sexual practice to those in monogamous marriage as the proper way to experience sexual satisfaction. Sexual activity requires risk as two persons make themselves completely vulnerable to one another. In marriage, two persons are committed to one another in a way which makes such vulnerability safe (Rubio 106-108). Because marriage and sexual relations reflect Christ’s love for the Church, couples sacrifice their own desires in order to satisfy their partner, just as Christ sacrificed Himself for the Church. Such sacrifice is required for mutual sexual satisfaction and is part of the marriage vows whereas it is not valued in casual scenarios (108-111).
Adultery is the opposite of self-sacrifice and breaks the trust required for vulnerability (114). The prophets also use adultery as a symbol of idolatry, of turning from God (CRC 2018 18; Ez. 16:14-22; Hos. 2:14-20). Joining one’s body to someone other than a spouse is a picture of unfaithfulness to God and is contrary to a Christian’s status as one who is united to Christ.
CRC Committee to Arciulate a Foundation-Laying Biblical Theology of Human Sexuality Prelimenary Report, 2019.
CRC Report 29: Marriage Guideline, Synod 1980.
Rubio, Julie Hanlon, Family Ethics: Practicies for Christians. Washington: Georgetown University Press, 2010.