Marriage is the agreement of a man and a woman to stay together in a romantic relationship until death, to continue to be joined together as one flesh.
And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female,
Matthew 19:4-6
And said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh?
Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder.
Becoming one flesh is the act of sexual union that Adam and Eve took part in after God separated the woman from the man and made her from his rib.
God only created the biological process of becoming one flesh. He did not create marriage. Marriage is purely for this time in our flesh, in heaven and in our spiritual bodies, marriage is no longer necessary.
“For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven.”
Matthew 22:30
Betrothed means the verbal agreement between spouses to be married. Sex is the consummation of the agreement. There is no need for any kind of ceremony or legal proceedings to be married in the eyes of the Lord.
Thou shalt betroth a wife, and another man shall lie with her: thou shalt build an house, and thou shalt not dwell therein: thou shalt plant a vineyard, and shalt not gather the grapes thereof
Deuteronomy 28:30
And he came up, and told his father and his mother, and said, I have seen a woman in Timnath of the daughters of the Philistines: now therefore get her for me to wife.
Judges 14:2
Now the birth of Jesus Christ was on this wise: When as his mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost.
Then Joseph her husband, being a just man, and not willing to make her a publick example, was minded to put her away privily.
Matthew 1:18-19
Fornication
The sin of fornication is romantic and sexual acts outside of the agreement to be married. The sin of adultery is romantic and sexual acts with another man or woman while betrothed or married.
And I will betroth thee unto me for ever; yea, I will betroth thee unto me in righteousness, and in judgment, and in lovingkindness, and in mercies.
Hosea 2:19
If any man take a wife, and go in unto her, and hate her,
1And give occasions of speech against her, and bring up an evil name upon her, and say, I took this woman, and when I came to her, I found her not a maid:
Then shall the father of the damsel, and her mother, take and bring forth the tokens of the damsel's virginity unto the elders of the city in the gate:
And the damsel's father shall say unto the elders, I gave my daughter unto this man to wife, and he hateth her;
And, lo, he hath given occasions of speech against her, saying, I found not thy daughter a maid; and yet these are the tokens of my daughter's virginity. And they shall spread the cloth before the elders of the city.
And the elders of that city shall take that man and chastise him;
And they shall amerce him in an hundred shekels of silver, and give them unto the father of the damsel, because he hath brought up an evil name upon a virgin of Israel: and she shall be his wife; he may not put her away all his days.
But if this thing be true, and the tokens of virginity be not found for the damsel:
Then they shall bring out the damsel to the door of her father's house, and the men of her city shall stone her with stones that she die: because she hath wrought folly in Israel, to play the whore in her father's house: so shalt thou put evil away from among you.
If a man be found lying with a woman married to an husband, then they shall both of them die, both the man that lay with the woman, and the woman: so shalt thou put away evil from Israel.
If a damsel that is a virgin be betrothed unto an husband, and a man find her in the city, and lie with her;
Then ye shall bring them both out unto the gate of that city, and ye shall stone them with stones that they die; the damsel, because she cried not, being in the city; and the man, because he hath humbled his neighbour's wife: so thou shalt put away evil from among you.
But if a man find a betrothed damsel in the field, and the man force her, and lie with her: then the man only that lay with her shall die:
But unto the damsel thou shalt do nothing; there is in the damsel no sin worthy of death: for as when a man riseth against his neighbour, and slayeth him, even so is this matter:
For he found her in the field, and the betrothed damsel cried, and there was none to save her.
If a man find a damsel that is a virgin, which is not betrothed, and lay hold on her, and lie with her, and they be found;
Then the man that lay with her shall give unto the damsel's father fifty shekels of silver, and she shall be his wife; because he hath humbled her, he may not put her away all his days.
Deuteronomy 22:13-29
If a man commits fornication with a woman, he shall endow her to be his wife or pay her father the equivalent dowry.
And if a man entice a maid that is not betrothed, and lie with her, he shall surely endow her to be his wife.
Exodus 22:16-17
If her father utterly refuse to give her unto him, he shall pay money according to the dowry of virgins.
Divorce
Divorce can only be initiated by a man for fornication, in the case of being betrothed, or adultery, while being married, additionally abuse of the woman by the man, (‘maid’ in the following verse) means she can go free from the marriage agreement.
Eye for eye, tooth for tooth, hand for hand, foot for foot, Burning for burning, wound for wound, stripe for stripe. And if a man smite the eye of his servant, or the eye of his maid, that it perish; he shall let him go free for his eye’s sake. And if he smite out his manservant’s tooth, or his maidservant’s tooth; he shall let him go free for his tooth’s sake.
Exodus 21:24-27
They say unto him, Why did Moses then command to give a writing of divorcement, and to put her away?
8He saith unto them, Moses because of the hardness of your hearts suffered you to put away your wives: but from the beginning it was not so.
And I say unto you, Whosoever shall put away his wife, except it be for fornication, and shall marry another, committeth adultery: and whoso marrieth her which is put away doth commit adultery.
Matthew 19:7-9
After a woman receives a bill of divorcement and leaves her first husband’s house, she is permitted to marry another man. The passage further specifies that if this second marriage ends in divorce or the second husband dies, her former husband is forbidden from remarrying her, as doing so would be considered an abomination
When a man hath taken a wife, and married her, and it come to pass that she find no favour in his eyes, because he hath found some uncleanness in her: then let him write her a bill of divorcement, and give it in her hand, and send her out of his house.
And when she is departed out of his house, she may go and be another man’s wife. And if the latter husband hate her, and write her a bill of divorcement, and giveth it in her hand, and sendeth her out of his house; or if the latter husband die, which took her to be his wife;
Her former husband, which sent her away, may not take her again to be his wife, after that she is defiled; for that is abomination before the LORD: and thou shalt not cause the land to sin, which the LORD thy God giveth thee for an inheritance.”
Deuteronomy 24:1-4