Negro Reuben Reason v. John Bridges, 1 Cranch 477

The Court refused to suffer Mr. Smith to be examined on oath as to his religious opinions, whether he was a Methodist, and whether the Methodists had religious scruples as to the legality of slavery. A witness was sworn, who testified that it was not an essential tenet of their religion that slavery was contrary to the divine law; but some of them were of that opinion. The Court refused to permit the witness to be asked whether it was the prevailing opinion among the people called Methodists, and decided that it was incumbent on the party challenging to show, either that it was an essential tenet of their religion, or was the individual opinion of the juror.