A more thorough explanation:

The Statute of Mortmain, also known as the Mortmain Statute, is a law that limits gifts and other dispositions of land to corporations, especially charitable ones. It also prohibits corporations from holding land in perpetuity.

In England, laws such as the Provisions of Westminster and Magna Carta required the Crown's authorization before land could vest in a corporation. The purpose was to prevent lands from being held by religious corporations in perpetuity. This type of restriction was not generally part of the common law in the United States, but it influenced the enactment of certain state laws restricting the amount of property that a corporation could hold for religious or charitable purposes.

For example, a wealthy individual may want to donate a piece of land to a charity. However, the Statute of Mortmain would prevent the charity from holding onto the land forever. Instead, the charity would have to sell the land or transfer it to another entity after a certain period of time.