the Prophet, peace and blessings be upon him, said: “Allah has forbidden the sale of wine, carrion, swine, and idols.” They said, “What about the fat of carrion? Ships are caulked with it, hides are treated with it, and people use it for lamps”—meaning, they make lamps from it. He said, “No; it is unlawful.” (1) That is, its sale is unlawful, even though it has some benefit. Yet the Prophet, peace and blessings be upon him, prohibited its sale because it is impure. Accordingly, we say: the sale of impure manure is invalid, even if we hold that it may be used as fertilizer.

The second category of fertilizer is that which has been contaminated with impurity. Its sale is permissible because it can be purified.

Similar to that is soil upon which an animal has urinated—where the urine of that animal is impure. The original state of this soil is purity, but impurity has come upon it, so it is deemed contaminated. Is it permissible to sell this contaminated soil before purifying it?

The answer is yes, it is permissible, because its impurity can be removed. This is like a person selling a garment contaminated with impurity. If he has such a garment and sells it to someone, the sale is valid; however, he must inform the buyer that it is contaminated, lest the buyer be deceived by it.

The third category is pure fertilizer, and its sale is lawful all the more so.

“Impure oils, but not oils contaminated with impurity …”

His statement, “impure oils,” refers, for example, to oils derived from the fat of carrion. Since carrion is impure, the oils extracted from its fat are impure as well. Thus, impure oils may not be sold. The evidence for this is the statement of the Prophet, peace and blessings be upon him: