Look up:
Isaac Backus 1724-1806, a leading Baptist preacher during the era of the American Revolution who campaigned against state-established churches in New England. starting with https://en.wikipedia.org/wiki/Isaac_Backus . .
and . .
John Leland 1754-1841, especially his 1791 sermon titled The Rights of Conscience Inalienable,
“Government has no more to do with the religious opinions of men than it has with the principles of mathematics. Let every man speak freely without fear, maintain the principles that he believes, worship according to his own faith, either one God, three Gods, no God or twenty Gods; and let government protect him in so doing….”
and,
"The notion of a Christian commonwealth should be exploded forever...Government should protect every man in thinking and speaking freely, and see that one does not abuse another. The liberty I contend for is more than toleration. The very idea of toleration is despicable; it supposes that some have a pre-eminence above the rest to grant indulgence, whereas all should be equally free, Jews, Turks, Pagans and Christians."
A Chronicle of His Time in Virginia.
starting with https://en.wikipedia.org/wiki/John_Leland_(Baptist)#Excerpts_from_his_writings