What does Genesis 34:7 mean?
Several things are happening in close connection at this point of the story. Jacob hears Dinah has been raped by Shechem (Genesis 34:1–5). He does nothing for the moment, waiting for his sons to return from the field. Hamor and Shechem arrive to talk to Jacob about allowing Shechem to marry Dinah (Genesis 24:6). Now Jacob's sons rush onto the scene.While working with the livestock, they have heard what happened to Dinah. This might have been via messengers from Jacob or through some other news. Their response is very different from what we were told of Jacob's first reaction. They are enraged about what has been done to their sister. Their view is that Shechem has done an outrageous, disgraceful thing, a thing that "must not be done." There is no sense in the brothers' response that Shechem's actions can be excused under any circumstances.
For the first time, Genesis describes something as being done "in Israel," identifying Dinah's rape as offense not just against her, but against the family and the nation it will become. In one sense, this is a positive development: God's promise to make a distinct people of Abraham's descendants is coming true. In another sense, this is a dangerous moment, as outrage on behalf of Dinah is being mixed with a form of tribal pride. What happens next will create consequences that echo through the rest of history.