Selling milk mixed with water

Question

I am a shopkeeper and do the work of selling milk, and I sell this milk after mixing water into it. Moreover, if anyone asks me whether water has been mixed into it or not, I immediately tell him: “Yes, I sell it after mixing water,” but I do not tell anyone the quantity. Please tell me whether mixing water into milk is permissible or not.

Answer

Those who buy milk pay the price of milk and buy it calling it milk. Even if they do not ask you whether you mix water or not, the transaction they make is for milk itself. Therefore do not mix water into it; and if you are to mix it, disclose to the buyers that it contains such-and-such an amount of water — then whoever wishes may buy, and whoever does not wish need not buy.

Source: Fatawa Mahmudiyya

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