Christian views on divorce find their basis both in biblical sources and in texts authored by the Church Fathers of the early Christian Church, who were unanimous in the teaching regarding the issue.
According to the synoptic Gospels, Jesus emphasized the permanence of marriage (see Mark 10 at verses 1 to 12, Matthew 19; Luke 16:18) but also its integrity. In the Gospel of Mark, Jesus says "Whosoever shall put away his wife, and marry another, committeth adultery against her. And if a woman shall put away her husband, and be married to another, she commits adultery." The Gospel of Luke adds that those who marry divorced persons also commit adultery, as recorded in Luke 16;18. 1 Corinthians 6:9–10 states that adulterers "shall not inherit the kingdom of God". The only lawful ground for divorce available to the innocent spouse is fornication, or adultery, on the part of the guilty mate, as recorded in Matthew 19:9. Nevertheless, The Shepherd of Hermas, an early Christian work on the subject, teaches that while fornication is the only reason that divorce can ever be permitted, remarriage with another person is forbidden to allow repentance and reconciliation of the husband and wife (those who refuse to forgive and receive their spouse are guilty of a grave sin). This Christian teaching is echoed in 1 Corinthians 7:10–11, which forbids divorce and states that those spouses who have deserted their husband/wife should return their partner; if that is absolutely impossible, the husband and wife should remain chaste.
Both in the Gospel of Matthew and of Mark, Jesus remembers and quotes Genesis 1:27 ("male and female created He them"), and Genesis 2:24 ("shall a man leave father and mother, and shall cleave to his wife: and they twaine shall be one flesh."). Paul the Apostle concurred but added an exception, interpreted according to Roman Catholicism as the Pauline privilege; this interpretation of Paul's words teaches that in the case of a non-Christian couple (neither party has ever received the sacrament of baptism) where one of the parties converts to Christianity and receives the sacrament of baptism, that party is allowed to enter into a Christian marriage if and only if the non-Christian spouse departs.
The Catholic Church prohibits divorce, and permits annulment (a finding that the marriage was not canonically valid) under a narrow set of circumstances. The Eastern Orthodox Church permits divorce and remarriage in church in certain circumstances, though its rules are generally more restrictive than the civil divorce rules of most countries. Most Protestant churches discourage divorce though the way divorce is addressed varies by denomination; for example, the United Church of Christ permits divorce and allows for the possibility of remarriage, while denominations such as the Mennonite Christian Fellowship and Evangelical Methodist Church Conference forbid divorce except in the case of fornication and do not allow for the remarriage of divorced persons.
With respect to Christian states, the Christian emperors Constantine and Theodosius restricted the grounds for divorce to grave cause, but this was relaxed by Justinian in the 6th century. After the fall of the empire, familial life was regulated more by ecclesiastical authority than civil authority.
Roman Catholic Church
Although marriage was not yet dogmatically defined sacrament, by the ninth or tenth century, the divorce rate had been greatly reduced under the influence of the Roman Catholic Church, which considered marriage to be instituted by God and Christ indissoluble by mere human action. Marriage was later dogmatically defined as a sacrament, beginning in 1208, when Pope Innocent III required members of another religious movement to recognize that marriage was a sacrament as a condition for being received back into the Catholic Church. In 1254, Catholics accused Waldensians of condemning the sacrament of marriage, "saying that married persons sin mortally if they come together without the hope of offspring". In 1439 the Council of Florence defined marriage as a sacrament, solidifying the development of doctrine from the previous twelve centuries and described marriage as 'insoluble' "since it signifies the indivisible union of Christ and the church." The passage follows, "Although the separation of bed is lawful on account of fornication, it is not lawful to contract another marriage since the bond of a legitimately contracted marriage is perpetual."