[Fertilizing Farmland with Human Excrement and the Excrement of Animals Whose Meat Is Not Eaten]

Answer – and Allah is the One who grants success:
- The Sacred Law has come forbidding close contact with impurity and getting moistened by it, and has made it obligatory to keep away from it. He the Exalted said: “And uncleanliness avoid” [al-Muddaththir:5], and: “And do not approach immoralities – what is apparent of them and what is concealed” [al-Anʿām:151].
- There is no problem in the permissibility of touching the hand of a polytheist if it is dry. The Prophet, May Allah bless him and his family and grant them peace, spread out his garment for one of the polytheists to sit on; and it is obvious that, when he sat on the garment, his feet would be in contact with it. It is well known in the works of sīrah that the Prophet, May Allah bless him and his family and grant them peace, lodged the delegation of Thaqīf in his mosque, and that polytheists used to enter the mosque to meet him.
- In light of what we have mentioned, we can say: If the excrement is dry and hardened, it is permissible to take it and use it to fertilize crops and trees, especially if its collection and distribution are done with a shovel and basket.
- This is from the perspective of taking it, transporting it, and distributing it in the field. As for using it as fertilizer for crops, they have ruled that it is not permissible to use impure things. What appears to me – and Allah knows best – is that it is permissible to fertilize with impure excrement.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2