Is it permissible to purchase milk from milk banks if the amount of milk is equivalent to four or fewer nursings, in order to avoid the commingling of lineages, knowing that suckling does not prohibit except with five nursings?

"Dealing with milk banks, both buying and selling, is a contemporary issue on which jurists have differed. The Islamic Fiqh Council has issued a fatwa prohibiting breastfeeding from milk banks. Reducing the number of feedings to four is not a practical solution to avoid the mixing of lineages, as the five prohibited feedings are not tied to the quantity of milk but to custom. The quantity of a single milk feeding might be equivalent to five customary feedings, making it difficult to precisely control the actual number of feedings, especially since milk often has preservatives or enhancers added to it, which further complicates the matter. If it were practically possible to avoid the mixing of lineages, then other health and jurisprudential concerns mentioned by the Fiqh Council must be taken into consideration."