The quote is from the Reverend Timothy Dwight, who was a prominent figure in the Federalist Party and the President of Yale College in the late 18th century. He is expressing his fear and opposition to the election of Thomas Jefferson, who was the candidate of the Democratic-Republican Party, in the "Revolution of 1800".
The context of the quote relates to the political and cultural divisions between the Federalist Party and the Democratic-Republican Party during the "Revolution of 1800". The Federalists, of which Dwight was a member, were generally more conservative and advocated for a strong central government, while the Democratic-Republicans, led by Jefferson, were more liberal and advocated for states' rights and a smaller, less powerful central government.
Dwight's fear that "the Bible would be cast into a bonfire" and "our holy worship changed into a dance of [French] Jacobin phrensy" reflects the Federalists' belief that the Democratic-Republicans, who were seen as more secular and influenced by the ideals of the French Revolution, would undermine traditional religious values and morals in the United States. This sentiment is also reflected in Alan Taylor's reading "The Internal Enemy: Slavery and War in Virginia, 1772-1832" where he writes "Federalists warned that the election of Jefferson would bring atheism and anarchy" (Taylor, pg. 59).
In addition, Dwight's reference to "Voltaire and the dragoons of Marat" highlights the Federalists' fear that the Democratic-Republicans would import the radical and violent ideas of the French Revolution to the United States. This fear is also reflected in Taylor's reading where he writes "Federalists warned that the election of Jefferson would bring the Reign of Terror to America" (Taylor, pg. 59).
Overall, Dwight's quote reflects the Federalists' fear and opposition to the political and cultural changes that they believed would occur if Thomas Jefferson and the Democratic-Republican Party came to power during the "Revolution of 1800".