Genesis 34 begins with Jacob's daughter, Dinah, being taken and sexually assaulted by Shechem, who is the son of the local ruler, Hamor. Shechem wanted to take her also then for his wife and asked Hamor to "get me this girl as my wife". Jacob and his sons were "filled with grief and fury" because of the disgraceful thing that was done to Dinah. Hamor came to Jacob and asked permission for his son to marry Dinah and also for his other sons to marry Jacob's daughters. Shechem himself also came to Jacob and his sons and asked, "let me find favor in your eyes... let me marry her.. I will give you whatever you ask".
But, Jacob's sons responded deceitfully and told them they would agree to give Dinah if all the men among them were circumcised. Hamor and his sons agreed and instructed the town council to have every man in the town circumcised. Then Jacob's sons came 3 days later, while the men's wounds were still sore, and slaughtered them all with their swords. They also plundered and looted all their wealth, heards, and even their wives and children as captives. Afterwards, Jacob was angry, saying " You have ruined me ! .. We are so few that they will join forces and crush us.. my entire household will be wiped out !"
Their only response was,"But why should we let him treat out sister like a prostitute?". They avenged the evil done to their sister, rather than allowing God to deal justly with Shechem.