Charles Ellicott Commentary Genesis 34:7

"And the sons of Jacob came in from the field when they heard it: and the men were grieved, and they were very wroth, because he had wrought folly in Israel in lying with Jacob`s daughter; which thing ought not to be done." — Genesis 34:7 (ASV)

He had wrought folly in Israel. — The great anger of Jacob’s sons agrees as completely with the general harshness of their characters as the silence of the father with his habitual thoughtfulness; but it was aroused by a great wrong. The use, however, of the term Israel to signify the family of Jacob as distinguished from his person belongs to the age of Moses, and is one of the proofs of the arrangement of these records having been his work. In selecting them, and weaving them together into one history, he would add whatever was necessary, and in the latter half of this verse we apparently have one such addition.