Oliver Wolcott quotes:

The Constitution enjoins an oath upon all the officers of the United States. This is a direct appeal to that God Who is the avenger of perjury. Such an appeal to Him is a full acknowledgement of His being and providence.

Knowledge and liberty are so prevalent in this country, that I do not believe that the United States would ever be disposed to establish one religious sect, and lay all others under legal disabilities. But as we know not what may take place hereafter, and any such test would be exceedingly injurious to the rights of free citizens, I cannot think it altogether superfluous to have added a clause, which secures us from the possibility of such oppression.