20. If you wish to replace one wife with another, and you have given one of them a fortune, take nothing back from it. Would you take it back fraudulently and sinfully?
21. And how can you take it back, when you have been intimate with one another, and they have received from you a solid commitment?
22. Do not marry women whom your fathers married, except what is already past. That is improper, indecent, and a bad custom.
23. Forbidden for you are your mothers, your daughters, your sisters, your paternal aunts, your maternal aunts, your brother’s daughters, your sister’s daughters, your foster-mothers who nursed you, your sisters through nursing, your wives’ mothers, and your stepdaughters in your guardianship-born of wives you have gone into-but if you have not gone into them, there is no blame on you. And the wives of your genetic sons, and marrying two sisters simultaneously. Except what is past. God is Oft-Forgiving, Most Merciful.
24. And all married women, except those you rightfully possess. This is God’s decree, binding upon you. Permitted for you are those that lie outside these limits, provided you seek them in legal marriage, with gifts from your property, seeking wedlock, not prostitution. If you wish to enjoy them, then give them their dowry-a legal obligation. You commit no error by agreeing to any change to the dowry. God is All-Knowing, Most Wise.
25. If any of you lack the means to marry free believing women, he may marry one of the believing maids under your control. God is well aware of your faith. You are from one another. Marry them with the permission of their guardians, and give them their recompense fairly-to be protected-neither committing adultery, nor taking secret lovers. When they are married, if they commit adultery, their punishment shall be half that of free women. That is for those among you who fear falling into decadence. But to practice self-restraint is better for you. God is Most Forgiving, Most Merciful.
26. God intends to make things clear to you, and to guide you in the ways of those before you, and to redeem you. God is Most Knowing, Most Wise.
27. God intends to redeem you, but those who follow their desires want you to turn away utterly.
28. God intends to lighten your burden, for the human being was created weak.
29. O you who believe! Do not consume each other’s wealth illicitly, but trade by mutual consent. And do not kill yourselves, for God is Merciful towards you.
30. Whoever does that, out of hostility and wrongdoing, We will cast him into a Fire. And that would be easy for God.
Here Gabriel is telling Muhammad what to teach the people. If you are a man who wants another wife, then you must give all the dowery back to her. You can not sleep with another and start a family with another woman, while keeping the wealth of your past wife. It is wrong and it was a practice being done.
Also men marrying their own mothers, must have been an ancestral custom of the past. Gabriel has taught Muhammad this is a thing society does not want to keep doing. All incest is FORBIDDEN by God now, and Gabriel makes this very clear.
Incest is forbidden not just for the indecency of it, but for also the medical reasons. Incest takes the dominant genes of the family and makes them mutated, so many children born of incest usually are disabled and impaired physically and mentally.
You may now not have a woman without courtship and eventual marriage, it is a sad societal custom of even today..and many women still get hurt from these men that use them physically and abandon them when bored with them. These are behaviors of men that have been grieving women for a very long time and it is time they stop, Muhammad is shown.
Do not lie, steal, commit rape, incest, and also do not be so lost without faith, to commit suicide. These are all things against God and will be judged accordingly to the person who did the deeds.