Matthew Poole and continuators on Genesis 29:28

28 And Jacob did so, and fulfilled her week: and he gave him Rachel his daughter to wife also .

It was not so strange that Laban should give, as that Iacob should take, not onely two Wives, but two Sisters to Wife, which seems to be against the law of Nature, and was expresly forbidden by God afterward, Levit. 18. 18. Though it be also true that God might dispense with his own institution, or permit such things in the Patriarchs upon special reasons, which are not to be drawn into example.