Matthew 13:49-50
49 This is what will happen when the world's time comes to an end. God will send his angels. They will put wicked people in one place. And they will put God's righteous people in a separate place. 50 The angels will throw the wicked people into the great fire. There those people will weep and they will bite their teeth together.’
13:50Biting their teeth together may have shown that they were angry. Or it may have shown they were in much pain.