It is a new trend nowadays and many people of various places have taken the example and have started the milk banks. In such banks, milk from nursing mother is bought and sold to the women who need it to give their children if there own milk is lacking, or they are sick or are too busy working, etc. What is the ruling on buying milk from these banks?
Shaykh Muhammad ibn Saalih al-‘Uthaymeen, may Allah preserve him, who said as follows:
This is haraam. It is not permissible to establish this kind of bank, because this is human milk, and the milk from different mothers will be mixed so that no one will know who is the mother. In Islam, drinking the milk of a woman creates the same relationship as does a close tie by blood (i.e., it has an effect on whom one may and may not marry, etc.). If the milk is of any kind other than human, then there is nothing wrong with milk banks.
And Allah knows best.