Religion began when the first scoundrel met the first fool.
-- Voltaire
Came across this quote looking for another reportedly from 18th century British political writer Samuel Johnson.
Religion is the last refuge of a scoundrel.
Johnson is also said to have replaced Religion with Patriotism (meaning a false Patriotism). I think Voltaire's quote is more accurate. Scoundrels use religion to cover the illegitimacy of their scams; it becomes a useful tool.