It's found in the Preamble, which is the Constitution's reason for being.
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defense, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.The first principle of nationhood (which is derived from the natural law; the good of the many is more perfect than the good of one) is the promotion of the common good, which is synonymous with "the general Welfare." The other principles highlighted are concommitant with the promotion of the Common Good, and are also principles of the natural law.
The first amendment forbids the establishment of a national church, but was not meant to foster a "separation of church and state," since many states had established Christian churches at the time of the writing of the Constitution.
There were also synagogue in the colonies as well.
Notice the use of "our posterity."
Our Founding Fathers meant their posterity (ours) that they wrote about, and not the general posterity.
I hope the American people shake their collective quilt and come to understand what was meant by "our posterity"