From President James Madison’s Speech on the Right of Suffrage:

“The right of suffrage is a fundamental Article in Republican Constitutions. The regulation of it is, at the same time, a task of peculiar delicacy.

“Allow the right exclusively to property, and the rights of persons may be oppressed. The feudal polity alone sufficiently proves it.

“Extend it equally to all, and the rights of property or the claims of justice may be overruled by a majority without property, or interested in measures of injustice. Of this abundant proof is afforded by other popular Govts. and is not without examples in our own…

“In a just & a free Government, therefore, the rights both of property & of persons ought to be effectually guarded…

“Should Experience or public opinion require an equal & universal suffrage for each branch of the Govt…a resource favorable to the rights of landed & other property, when its possessors become the Minority, may be found in an enlargement of the Election Districts for one branch of the Legislature, and an extension of its period of service [the U.S. Senate]. Large districts are manifestly favorable to the election of persons of general respectability, and of probable attachment to the rights of property…The tendency of a longer period of service would be, to render the Body more stable in its policy, and more capable of stemming popular currents taking a wrong direction, till reason & justice could regain their ascendancy.”

[bracketed insert and emphases mine]

The U.S. Senate was created to supply a more stable institution to balance the more frequently elected, more volatile House of Representatives. Also note that the Senate, created to represent the “rights of landed & other property”, cannot initiate bills dealing with money (revenue). That is reserved to the House only.