Sayyidina Abyad ibn Hammal reported that he went to Allah’s Messenger (SAW) and requested that a salt mine be assigned to him. So, he gave him the mine. When he turned to go, someone in the assembly asked, “Do you know what you have given him. It is a perpetual source of ready water,” (meaning that it would produce plenty of salt). The narrator said that the Prophet (SAW) took it back from him. He then asked about the land of thorny trees that could be surrounded. The Prophet (SAW) said, “The land where the camels cannot go”, (meaning that place which is away from grazing ground).
[Abu Dawud 3064, Ibn e Majah 2475]