I give you the words of James Madison, the author of the Constitution, regarding what general welfare means from the Virginia Resolution of 1798 and the Tenth Amendment.
That this Assembly doth explicitly and peremptorily declare, that it views the powers of the federal government, as resulting from the compact, to which the states are parties; as limited by the plain sense and intention of the instrument constituting the compact; as no further valid that they are authorized by the grants enumerated in that compact; and that in case of a deliberate, palpable, and dangerous exercise of other powers, not granted by the said compact, the states who are parties thereto, have the right, and are in duty bound, to interpose for arresting the progress of the evil, and for maintaining within their respective limits, the authorities, rights and liberties appertaining to them.
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.