Lord Jesus Christ ‘warned’ never to call anybody a “fool!” as this verse states (in ‘full’):

“But I tell you that anyone who is angry with his brother will be subject to judgment. Again, anyone who says to his brother, ‘Raca,’ will be subject to the Sanhedrin. But anyone who says, ‘You fool!’ will be subject to the fire of hell.” (Matthew 5:22)

Why?

He said if you do —> call others a ‘fool’ —> you’ll be in danger of —> “Hell Fire”.

P/S:

I’m pretty sure He wasn’t ‘joking’.