Is it permissible for a married woman to contract herself for breastfeeding without her husband's permission?
Chapter on Who is More Entitled to Child Custody
Al-Mughni
Book of Maintenance (Nafaqāt)
Primary text
If a married woman contracts herself for breastfeeding without the permission of her husband, the contract is invalid. This is because the contract entails the forfeiture of her husband's right. This constitutes one of the two views held by the companions of Al-Shafi'i. The primary evidence asserts that it is a contract that results in the forfeiture of a right established by a prior contract, rendering it invalid, analogous to the contract of a tenant leasing out what has already been leased to him.
Supporting text
The other view held by some companions of Al-Shafi'i maintains that it is valid because it pertains to a subject matter distinct from the contract of marriage, although the husband retains the right to annul it because it interferes with the right to marital enjoyment and causes disorder.