Tafsir of verse 12
Al-Mukhtasar
You have half of what your wives leave, if they have no child. If they have a child, whether it is your child or not, then you get a fourth of the wealth they leave, after any bequest they have made and the repayment of any debts they had. Wives get a quarter of what you leave, if you have no child, whether it is their child or not. If you have a child, then they get an eighth of what you leave, after any bequest you have made and the repayment of any debts you had. If someone dies without any parents or children to inherit from them, but they have a brother or sister from the same mother as them, then each of them gets a sixth. If they have more than one brother or sister from the same mother as them, then they share a third, with brothers and sisters receiving the same share – this is after any bequest that they leave and the repayment of any debts they had, with the condition that the bequest does not cause harm to any of the inheritors, such as it being more than a third of the total of the wealth. The rulings contained in the verses about inheritance law are an obligation on you, and Allah knows what is in the interests of His servants in this world and the Afterlife. He is forbearing, and not quick to punish.
Tafsir of the whole Surah An-Nisa
Other translations of verse 12
Your share is half of your wives’ estate if they leave no child; but if they leave a child, you get one-fourth, after settling the bequests or debts. Your wives’ share is one-fourth of your estate if you leave no child, but if you leave a child, they get one-eighth, after settling the bequests or debts. If a man or a woman leaves neither parents nor offspring10, but has a brother or a sister, each one gets one-sixth11; but if they are more than two, they share in one-third, after settling the bequests or debts, without causing harm to the heirs. This is an instruction from Allah; and Allah is All-Knowing, Most Forbearing.
Notes
[10] Kalālah: A person who has no living children or parents; (from iklīl), wreath, as his brothers and sisters surround him like a wreath surrounds the head.
[11] These shares are divided equally between males and females.
In that which your wives leave, your share is a half if they have no child; but if they leave a child, you get a fourth of that which they leave after payment of legacies that they may have bequeathed or debts. In that which you leave, their (your wives) share is a fourth if you leave no child; but if you leave a child, they get an eighth of that which you leave after payment of legacies that you may have bequeathed or debts. If the man or woman whose inheritance is in question has left neither ascendants nor descendants, but has left a brother or a sister, each one of the two gets a sixth; but if more than two, they share in a third, after payment of legacies he (or she) may have bequeathed or debts, so that no loss is caused (to anyone). This is a Commandment from Allâh; and Allâh is Ever All-Knowing, Most-Forbearing.
And unto you belongeth a half of that which your wives leave, if they have no child; but if they have a child then unto you the fourth of that which they leave, after any legacy they may have bequeathed, or debt (they may have contracted, hath been paid). And unto them belongeth the fourth of that which ye leave if ye have no child, but if ye have a child then the eighth of that which ye leave, after any legacy ye may have bequeathed, or debt (ye may have contracted, hath been paid). And if a man or a woman have a distant heir (having left neither parent nor child), and he (or she) have a brother or a sister (only on the mother's side) then to each of them twain (the brother and the sister) the sixth, and if they be more than two, then they shall be sharers in the third, after any legacy that may have been bequeathed or debt (contracted) not injuring (the heirs by willing away more than a third of the heritage) hath been paid. A commandment from Allah. Allah is Knower, Indulgent.
In what your wives leave, your share is a half, if they leave no child; but if they leave a child, ye get a fourth; after payment of legacies and debts. In what ye leave, their share is a fourth, if ye leave no child; but if ye leave a child, they get an eighth; after payment of legacies and debts. If the man or woman whose inheritance is in question, has left neither ascendants nor descendants, but has left a brother or a sister, each one of the two gets a sixth; but if more than two, they share in a third; after payment of legacies and debts; so that no loss is caused (to any one). Thus is it ordained by Allah; and Allah is All-knowing, Most Forbearing.
And you shall have half of what your wives leave if they have no child, but if they have a child, then you shall have a fourth of what they leave after (payment of) any bequest they may have bequeathed or a debt; and they shall have the fourth of what you leave if you have no child, but if you have a child then they shall have the eighth of what you leave after (payment of) a bequest you may have bequeathed or a debt; and if a man or a woman leaves property to be inherited by neither parents nor offspring, and he (or she) has a brother or a sister, then each of them two shall have the sixth, but if they are more than that, they shall be sharers in the third after (payment of) any bequest that may have been bequeathed or a debt that does not harm (others); this is an ordinance from Allah: and Allah is Knowing, Forbearing.
And for you is a half of whatever your spouses have left, in case they have no children; (yet) in case they have children, then for you is the fourth of whatever they have left, (only) after any bequest they may have bequeathed, (Literally: enjoined) or any debt. And for them is a fourth of whatever you have left, in case you have no children; yet in case you have children, then they have an eighth of whatever you have left, (only) after any bequest you may have bequeathed, or any debt. And in case a man or a woman has no heir direct, and has a brother or a sister, then to each one of the two is the sixth; yet in case they are more numerous than that, then they shall be sharers in the third, (only) after any bequest may have been bequeathed, or any debt, without harming (others). (This is) an injunction from Allah; and Allah is Ever-Knowing, Ever-Forbearing.