Is divorce allowed?
He who created them from the beginning made them male and female, and said, 'For this cause a man shall leave his father and his mother, and shall cleave to his wife; and the two shall become one flesh'. Consequently they are no longer two, but one flesh. What God has joined together, let no man separate.
(Matt 19:4-6)

Because of your hardness of heart Moses permitted you to divorce your wives;
(Matt 19:8)

To divorce and remarry is to commit adultery:
Everone who divorces his wife and marries another commits adultery; and he who marries one who is divorced from a husband commits adultery.
(Luke 16:18)

Whoever divorces his wife, except for immorality, and marries another woman commits adultery.
(Matt19:9)

Whoever divorces his wife and marries another woman commits adultery against her; and if she herself divorces her husband and marries another man, she is committing adultery.
(Mark 10:11-12)

The married woman is bound by law to her husband while he is living; ... if, while her husband is living, she is joined to another man, she shall be called an adulteress;
(Rom 7:2-3)

To divorce a woman forces her to become an adulteress:
....everyone who divorces his wife, except for the cause of unchastity, makes her commit adultery; and whoever marries a divorced woman commits adultery.
(Matt 5:32)
[In our society divorcing a woman may not force her into adultery - she can remain single]

Paul reiterates the Lord's instructions:
To the married I give instructions, not I, but the Lord, that the wife should not leave her husband (but if she does leave, let her remain unmarried, or else be reconciled to her husband), and that the husband should not send his wife away.
(1 Cor 7:10-11)

What about a non-Christian partner?
If any brother has a wife who is an unbeliever, and she consents to live with him, let him not send her away. And a woman who has an unbelieving husband, and he consents to live with her, let her not send her husband away. For the unbelieving husband is sanctified through his wife, and the unbelieving wife is sanctified through her believing husband; for otherwise your children are unclean, but now they are holy.
(1 Cor 7:12-14)

If the non-Christian leaves?
Yet if the unbelieving one leaves, let him leave; the brother or the sister is not under bondage in such cases, but God has called us to peace.
(1 Cor 7:15)

Another reason to stay together:
For how do you know, O wife, whether you will save your husband? Or how do you know, O husband, whether you will save your wife?
(1 Cor 7:16)

A widow may remarry:
A wife is bound as long as her husband lives; but if her husband is dead, she is free to be married to whom she wishes, only in the Lord.
(1 Cor 7:39)

Should she?
But in my opinion she is happier if she remain as she is; and I think that I also have the Spirit of God.
(1 Cor 7:40)
[This may be influenced by the 'present distress' of v26]

Therefore, I want younger widows to get married, bear children, keep house, and give the enemy no occasion for reproach;
(1 Tim 5:14)
[Here younger is less than 60 years old - see 1 Tim 5:9]