Breastfeeding (al-riḍāʿah) is a traditionally widespread phenomenon in Islamic culture. As breastfeeding of other than the own biological children establishes a foster relationship which leads to the prohibition of marriage (taḥrῑm) between the breastfed infant, the wet nurse, and a specified number of other persons, there are several religious legal and cultural inhibitions among Muslims regarding the use of donor milk from unidentified sources. This article provides an insight into the reception of milk banks in the Islamic world as against the culturally unique background of foster relations.