The letter was the subject of intense scrutiny by Jefferson, and he consulted some of New England politicians to be sure that his words would not offend the Baptists while still conveying his message: it was not the place of Congress or the Executive branch to do anything that might be misconstrued as the establishment of a state religion.
Now for my need to post some quotes.
"The cause of America is in a great measure the cause of all mankind.
Where, some say, is the king of America? I'll tell you, friend, He reigns
William Penn (Founder of Pennsylvania)
"If thou wouldst rule well, thou must rule for God, and to do that, thou must be
ruled by him....Those who will not be governed by God will be ruled by tyrants."
Daniel Webster (Statesman, Lawyer, Orator)
"Finally, let us not forget the religious character of our origin. Our fathers were brought hither by their high veneration for the Christian religion. They journeyed by its light, and labored in its hope. They sought to incorporate its principles with the elements of their society, and to diffuse its influence through all their institutions, civil, political, or literary.
June 21, 1776
"Statesmen, my dear Sir, may plan and speculate for liberty, but it is
Religion and Morality alone, which can establish the Principles upon which
Freedom can securely stand.
Hat tips to the following for aiding in my information gathering -