John 4:18
because you have had five husbands, and the man you are now living with is not [really] your husband. So, you have told the truth."
Mark 10:12
And if she herself divorces her husband and marries another [man], she commits sexual unfaithfulness [toward him]."
Romans 7:3
So, if she lives with another man while her husband is still alive, she will be called an adulteress [i.e., a person who is sexually unfaithful to their mate]. But if her husband dies, she is legally free to marry another man without committing adultery.
1 Corinthians 7:10-11
Now I command married people, although it is [really] the Lord's command [See. Mark 10:2-12]: A wife should not separate from her husband. [Note: This act implies the intention of pursuing a legal and permanent breach of the marriage relationship by divorce. "Separate" and "divorce" appear to be used interchangeably in this section. See verses 11-15].
Hebrews 13:4
Marriage should be considered honorable among all people and its sexual responsibilities should be faithfully kept. For God will judge [and condemn] those people who are sexually immoral and who are sexually unfaithful to their mates.