Term of the Senate, [26 June] 1787

In England, at this day, if elections were open to all classes of people, the property of the landed proprietors would be insecure. An agrarian law would soon take place. If these observations be just, our government ought to secure the permanent interests of the country against innovation. Landholders ought to have a share in the government, to support these invaluable interests and to balance and check the other. They ought to be so constituted as to protect the minority of the opulent against the majority. The senate, therefore, ought to be this body; and to answer these purposes, they ought to have permanency and stability.

http://founders.archives.gov/documents/Madison/01-10-02-0044