How is the surplus distributed among sisters of different degrees (full, consanguineal, uterine) when no agnates are present?
Chapter on the Roots of Inheritance Shares that Increase (Awl)
Al-Mughni
Book of Inheritance Shares (Farā'id)
Primary text
If the mother, consanguineal sister, and uterine sister remain, the mother takes one-sixth, the consanguineal sister takes one-sixth, and the uterine sister takes one-sixth. The remainder is returned to them according to their shares. The distribution results in five shares: the mother and consanguineal sister each receive three-fifths of the remaining portion, and the uterine sister receives one-fifth.