It is not permissible to convert kharaj land into ʿushr land, nor ʿushr land into kharaj land. Aḥmad was asked, according to the report of Isḥāq, about Dār al-Baṭṭīkh in Tarsus: “It was Bīrūmā, and whatever had been imposed on it remained due from it, extending from al-Armanī to beyond the trench.” Kharaj was imposed upon it, and he said: “The collectors had not levied kharaj on it when it had not been subject to kharaj; now that kharaj has been imposed upon it, it is not to be changed.” He said, “They did well,” for he had objected to imposing kharaj on land that had not previously borne it.

If ʿushr land is irrigated with kharaj water, the levy taken from it is ʿushr. If kharaj land is irrigated with ʿushr water, the levy taken from it is kharaj, on the basis that consideration is given to the land rather than the water. According to Abū Ḥanīfah, however, consideration is given to the water. Thus, when ʿushr land is irrigated with kharaj water, kharaj is collected from it; and when kharaj land is irrigated with ʿushr water, ʿushr is collected from it—on the basis that consideration is given to the water rather than the land. Giving consideration to the land is preferable to giving consideration to the water, because kharaj is levied on the land, whereas ʿushr is levied on the crop. No kharaj or ʿushr is due on the water itself, so it should not be the basis for either levy.

On the basis of this disagreement, Abū Ḥanīfah prohibited the owner of kharaj land from irrigating it with ʿushr water, and prohibited the owner of ʿushr land from irrigating it with kharaj water. Aḥmad, however, did not prohibit either of them from irrigating with whichever of the two waters he wished. Aḥmad said, according to the report of Ṣāliḥ, “Kharaj is imposed on the land itself.” According to the report of Ibn Manṣūr, he said, “It is merely a jizya on the land itself.” The report of Ibn Manṣūr thus makes clear that kharaj is levied on the land itself, while the report of Ṣāliḥ states that it is imposed on the land, like a jizya imposed on a person. This entails that it is levied on the land itself. Since kharaj is due on the land itself, consideration is given to the land, not to the water with which it is irrigated.

If houses and shops are built on kharaj land, the kharaj of the land remains due, because the landowner is entitled to use it as he wishes.