What is meant by the Hadith: "The Messenger of Allah (peace be upon him) only ordained pre-emption for everything that has not been divided, but if boundaries are set and roads allocated, then there is no pre-emption"?

If one of the partners sells his share of a joint property, the other partner has the right of pre-emption to acquire it for the same price, in order to prevent the harm of partnership. This right is established as long as the property has not been divided, its boundaries defined, and its access routes arranged. If these actions are completed, then there is no right of pre-emption because its cause has ceased to exist.