Nedarim

We learnt: [If one says to his wife, 'Konam be] that which you benefit from me until Passover, if you go to your father's house until the Festival',  if she went before Passover, she may not benefit from him until Passover. Now, only if she went before Passover is she forbidden, but not otherwise?  — R. Abba answered: If she went before Passover, she is forbidden and is flagellated;  If she did not go, she is merely forbidden. Then consider the second clause: After Passover, she is subject to he shall not break his word. Now if she did not benefit before Passover, how can the injunction apply? Hence it is obvious that she did benefit, which proves that this is permitted,