In this week's parsha (Bereishit 31:32), Yaakov says that whoever stole Lavan's idols will not live, not knowing that Rachel had taken them.
The question is, was this said as a curse or a neder (vow)? Because if it was a neder, he could have had it annulled, with the easy out of "i didn't know it was my favorite wife". And if it was a neder, why didn't he have it annulled?