On avenging a killing

i am enjoying the book “Review of the ‘Anizah Tribe”: “An avenger should not kill the aggressor while asleep and he usually wakes him up to remind him of his evil deed before dispatching him. He then slits the corners of his mouth up to the ears, cuts off his ears and put them in his mouth to show that it is a killing of vengeance. He who unintentionally kills a man is not subject to vengeance unless he refuses to pay the compensation.” I will keep to the horses, thank you.