Sayyiduna Abyad bin Hammal (may Allah be pleased with him) came in a delegation to the Prophet (peace and blessings be upon him) and asked him for the salt mine. Ibn al-Mutawakkil (may Allah have mercy on him) said: the one at Ma'rib. He (peace and blessings be upon him) gave it to him. When he turned to leave, a man from the gathering said: Do you know what you have given him? You have given him ever-flowing water. So the Messenger of Allah (peace and blessings be upon him) took it back. The narrator says: I asked him what part of the arak trees may be made a protected pasture, and he (peace and blessings be upon him) said: "What the hooves do not reach." Ibn al-Mutawakkil (may Allah have mercy on him) said: the hooves of camels.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب إحياء الموات / 11828