Al-Hakam said that Sayyiduna Umar (may Allah be pleased with him) sent Sayyiduna Uthman bin Hunayf (may Allah be pleased with him) to the place called the Sawad, and he fixed on every cultivated and uncultivated field that water reaches one qafiz (a measure) and a dirham. Waki' said: That is, of wheat and barley. And on every field of grapevines he fixed ten dirhams, and on fresh dates five dirhams.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18383