The Federalist, No. XXXIII. [Hamilton.] (January 3, 1788)

But /smcap suspicion may ask, Why then was it [Art. I, Sect. 8, last paragraph] introduced? The answer is, that it could only have been done for greater caution, and to guard against all cavilling refinements in those who might hereafter feel a disposition to curtail and evade the legitimate authorities of the union. The convention probably foresaw, that it has been a principal aim of these papers to inculcate, that the danger which most threatens our political welfare is, that the state governments will finally sap the foundations of the union; and might therefore think it necessary, in so cardinal a point, to leave nothing to construction. Whatever may have been the inducement to it, the wisdom of the precaution is evident from the cry which has been raised against it;1 as that very cry betrays a disposition to question the great and essential truth which it is manifestly the object of that provision to declare.