Quote from FredFlash:
Founding Father James Madison considered it a pure sacred and truly Christian principle ordained by the Savior in Matthew 22:21. See his "Detached Memoranda" where he refers to anything less than the perfect separation of church and state as a vilolation of Matthew 22:21
If some of the States have not embraced this just and this truly Xn principle in its proper latitude, all of them present examples by which the most enlightened States of the old world may be instructed; and there is one State at least, Virginia, where religious liberty is placed on its true foundation and is defined in its full latitude...
Ye States of America, which retain in your Constitutions or Codes, any aberration from the sacred principle of religious liberty, by giving to Caesar what belongs to God, or joining together what God has put asunder, hasten to revise & purify your systems, and make the example of your Country as pure & compleat, in what relates to the freedom of the mind and its allegiance to its maker, as in what belongs to the legitimate objects of political & civil institutions.
Founding Father Isaac Backus also believe that the Separation of Church and State was ordained in Matthew 22:21.
We view it to be our incumbent duty, to render unto Caesar the things that are his, but that it is of as much importance not to render unto him any thing that belongs only to God, who is to be obeyed rather than man. And as it is evident to us, that God always claimed it as his sole prerogative to determine by his own laws, what his worship shall be, who shall minister in it, and how they shall be supported...