And the enumerated powers include:
The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States;
To borrow money on the credit of the United States;
The enumerated powers there are to lay and collect taxes, duties, imposts and excises. Paying debts, providing for the common defense and general welfare are goals, not enumerated powers. So meeting those goals has to be done within the confines of other enumerated powers. Note the Constitutions enumeration of powers regarding defense issues. Here is what Madison said regarding the general welfare:
Money cannot be applied to the General Welfare, otherwise than by an application of it to some particular measure conducive to the General Welfare. Whenever, therefore, money has been raised by the General Authority, and is to be applied to a particular measure, a
question arises whether the particular measure be within the enumerated authorities vested in Congress. If it be, the money requisite for it may be applied to it; if it be not, no such application can be made.
And here's what Jefferson said about the same issue:
[O]ur tenet ever was, and, indeed, it is almost the only landmark which now divides the federalists from the republicans, that
Congress has not unlimited powers to provide for the general welfare, but were to those specifically enumerated; and that, as it was never meant they should raise money for purposes which the enumeration did not place under their action; consequently, that the specification of powers is a limitation of the purposes for which they may raise money.
And yet more for Madison:
If Congress can do whatever in their discretion can be done by money, and will promote the General Welfare, the Government is no longer a limited one, possessing enumerated powers, but an indefinite one, subject to particular exceptions.