A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
gen 34:1THE DISHONOR OF DINAH. (Gen. 34:1-31)
Though freed from foreign troubles, Jacob met with a great domestic calamity in the fall of his only daughter. According to JOSEPHUS, she had been attending a festival; but it is highly probable that she had been often and freely mixing in the society of the place and that she, being a simple, inexperienced, and vain young woman, had been flattered by the attentions of the ruler's son. There must have been time and opportunities of acquaintance to produce the strong attachment that Shechem had for her.
gen 34:5Jacob held his peace--Jacob, as a father and a good man, must have been deeply distressed. But he could do little. In the case of a family by different wives, it is not the father, but the full brothers, on whom the protection of the daughters devolves--they are the guardians of a sister's welfare and the avengers of her wrongs. It was for this reason that Simeon and Levi, the two brothers of Dinah by Leah [Gen 34:25], appear the chief actors in this episode; and though the two fathers would have probably brought about an amicable arrangement of the affair, the hasty arrival of these enraged brothers introduced a new element into the negotiations.
gen 34:6Hamor--that is, "ass"; and it is a striking proof of the very different ideas which, in the East, are associated with that animal, which there appears sprightly, well proportioned, and of great activity. This chief is called Emmor (Act 7:16).
gen 34:7the men were grieved, and . . . very wroth--Good men in such a case could not but grieve; but it would have been well if their anger had been less, or that they had known the precept "let not the sun go down upon your wrath" [Eph 4:26]. No injury can justify revenge (Deu 32:35; Rom 12:9); but Jacob's sons planned a scheme of revenge in the most deceitful manner.
gen 34:8Hamor communed with them--The prince and his son seem at first sight to have acted honestly, and our feelings are enlisted on their side. They betray no jealousy of the powerful shepherds; on the contrary, they show every desire to establish friendly intercourse. But their conduct was unjustifiable in neither expressing regret nor restoring Dinah to her family; and this great error was the true cause of the negotiations ending in so unhappy a manner.
gen 34:11Shechem said unto her father . . . and brethren--The consideration of the proposal for marriage belonged to Jacob, and he certainly showed great weakness in yielding so much to the fiery impetuosity of his sons. The sequel shows the unhappy consequences of that concession.
gen 34:12Ask me never so much dowry and gift--The gift refers to the presents made at betrothal, both to the bride elect and her relations (compare Gen 24:53), the dowry to a suitable settlement upon her.
gen 34:13The sons of Jacob answered--The honor of their family consisted in having the sign of the covenant. Circumcision was the external rite by which persons were admitted members of the ancient Church. But that outward rite could not make the Shechemites true Israelites; and yet it does not appear that Jacob's sons required anything more. Nothing is said of their teaching the people to worship the true God, but only of their insisting on their being circumcised; and it is evident that they did not seek to convert Shechem, but only made a show of religion--a cloak to cover their diabolical design. Hypocrisy and deceit, in all cases vicious, are infinitely more so when accompanied with a show of religion; and here the sons of Jacob, under the pretense of conscientious scruples, conceal a scheme of treachery as cruel and diabolical as was, perhaps, ever perpetrated.
gen 34:20Hamor and Shechem . . . came unto the gate of their city--That was the place where every public communication was made; and in the ready obsequious submission of the people to this measure we see an evidence either of the extraordinary affection for the governing family, or of the abject despotism of the East, where the will of a chief is an absolute command.
gen 34:30Jacob said . . . Ye have troubled me--This atrocious outrage perpetrated on the defenseless citizens and their families made the cup of Jacob's affliction overflow. We may wonder that, in speaking of it to his sons, he did not represent it as a heinous sin, an atrocious violation of the laws of God and man, but dwelt solely on the present consequences. It was probably because that was the only view likely to rouse the cold-blooded apathy, the hardened consciences of those ruffian sons. Nothing but the restraining power of God saved him and his family from the united vengeance of the people (compare Gen 35:5). All his sons had not been engaged in the massacre. Joseph was a boy, Benjamin not yet born, and the other eight not concerned in it. Simeon and Levi alone, with their retainers, had been the guilty actors in the bloody tragedy. But the Canaanites would not be discriminating in their vengeance; and if all the Shechemites were put to death for the offense of their chief's son, what wonder if the natives should extend their hatred to all the family of Jacob; and who probably equalled, in number, the inhabitants of that village.