The Quran Verses
Surah 4:11:
Allah instructs you concerning your children: for the male, what is equal to the share of two females... And for one's parents, to each one of them is a sixth of his estate if he left children...Surah 4:12:
...And for you is half of what your wives leave if they have no child. But if they have a child, for you is one fourth of what they leave...Surah 4:24:
(Often grouped with the rules of wives' shares, though the 1/8th rule is in 4:12)
Let us look at a specific scenario commanded by these verses: A man dies leaving behind a wife, three daughters, and two parents.
According to Surah 4:11-12, the shares are:
Wife: 1/8
Daughters (two or more): 2/3
Mother: 1/6
Father: 1/6
The Relevant Source Text (Basic Mathematics)
1/8 + 2/3 + 1/6 + 1/6
Converted to a common denominator of 24:
3/24 (Wife) + 16/24 (Daughters) + 4/24 (Mother) + 4/24 (Father)
Total = 27/24!
The fractions add up to more than 100% (1.125 or 27/24).
This is a glaring mathematical impossibility. Ann omniscient God who created the laws of mathematics would not make a basic fractional error in distributing an estate.
Islamic jurists realized this error after Muhammad's death during the reign of Caliph Umar. To fix it, they had to invent a human legal workaround called "Awl" (proportional reduction) to shrink everyone's shares so the estate could be divided.
The necessity of human intervention to fix God's math proves the text is of flawed human origin.