The four Sunni schools accept the doctrine of `awl, the rule that all the shares will be diminished proportionately, exactly like the creditors’ claims when the assets fall short of meeting them. Hence if the heirs are wife, parents and two daughters, according to these schools it will be an instance of ‘awl. The obligation is met by dividing the heritage into 27 parts, though it earlier comprised 24 parts. The wife will take 3/27 (i.e. her share becomes 1/9 instead of 1/8), the parents take 8/27 and the daughter 16/27. The Imāmīs do not accept the doctrine of ‘awl and keep the corps (in the previous example) fixed at 24 parts by diminishing the share of the two daughters. Hence the wife takes her complete share of 1/8 (which is 3/24), the parents take 1/3 (which is 8/24), and the remainder goes to the two daughters.
The four schools argue in favour of the validity of ‘awl and the reduction of all the shares by citing the precedent of a woman who died during the reign of the Second Caliph, ‘Umar, leaving behind husband and two agnate sisters. The Caliph gathered the Companions and said: “The shares determined by God for the husband and the two sisters are a half and two-thirds respectively. Now if I start with the husband’s share, the two-thirds will not remain for the two sisters, and if I start with the two sisters, the half will not remain for the husband. So give me advice.”
Some advised him to follow ‘awl by diminishing all the shares pro portionately, while Ibn ‘Abbas vehemently opposed it. But ‘Umar did not accept his view and acted according to the opinion of others, telling the heirs: “I do not see any better way regarding this estate but to distribute it amongst you in proportion to your shares.” Hence ‘Umar was the first person to apply ‘awl to the shares and all the Sunni schools followed him.