Question: Some of the manufactured cheese in the Christian lands states that in its preparation there is rennet from a calf. So is this rennet impermissible following its origin, if most likely, it is not slaughtered in the shariah manner?
Answer: “No, because the action of the Companions was eating cheese, which came to them from the lands of the Persia.
Rennet is impure and impermissible when it is from an animal not slaughtered upon the Islamic manner. So there is no difference here between rennet of an animal which is slaughtered and is permissible and if it is not slaughtered and is not permissible.
However, the action of the Companions was eating cheese, which came to them from Persia. A chapter of fiqh opens for us that few enter into. This rennet is thrown in a great amount of milk. So imagine pure water sent from the sky and the likes of this impurity falls into it, so is it allowed to drink this water and purify with it? Yes, it is permissible because the impurity which falls in it did not overcome it. Thus, the water retains its title: pure and purifying.
Likewise, this milk [which has rennet] is pure and permissible to drink.
If this milk, which impure rennet is thrown into it, becomes cheese, so here I cannot give a certain opinion, but if some chemists examine for us that this cheese changed to another material, (ie. changed to another reality), so if the affair is like that, then the affair is easy.
If the a investigator clarifies that the rennet does not continue to retain its reality, however it is lost in the quantity of milk which turned to cheese, then the answer has preceded…”
[Fataawa al-Madinah no. 86 s cited in al-Masaail al-‘ilmiyyah wa Fatawaa ash-Shar’iah Fatawaa Shaikh al-‘Allamah Muhammad Nasruddin al-Albani fi Madinah wal-‘Emaraat (pg.173-174)]
Faisal bin Abdul Qaadir bin Hassan