“Of all the dispositions and habits which lead to political prosperity, religion and morality are indispensable supports.”
- George Washington during his farewell address.

A few more quotes from other founding fathers.
“We have no government armed in power capable of contending in human passions unbridled by morality and religion. Our constitution was made only for a moral and religious people. It is wholly inadequate for the government of any other.”
- Samuel Adams, Source: Unknown

“The highest glory of the American Revolution was that it connected in one indissoluble bond, the principles of civil government with the principles of Christianity.

all via Quoty.