Vonnegut was not a Christian, though he spoke of Jesus as “the greatest and most humane of human beings.” In a talk he gave to St. Clement Episcopal Church in New York City (“ Palm Sunday”), he said: “I am enchanted by the Sermon on the Mount. Being merciful, it seems to me, is the only good idea we have had so far. Perhaps we will get another good idea by and by— and then we will have two good ideas.”

Sermon On The Mount
Csaba Osvath

Vonnegut, Kurt (2013-04-11). If This Isn’t Nice, What Is?: Advice for the Young (Kindle Locations 89-92). RosettaBooks. Kindle Edition.