´It was narrated that Ibn 'Umar said:` "The Messenger of Allah said: 'Whoever swears an oath and says: If Allah wills, then he has made an exception.'"
Hadith Referenceسنن نسائي / كتاب الأيمان والنذور / 3860
´It was narrated from Ibn 'Umar that the Messenger of Allah said:` "Whoever swears an oath and says, 'If Allah wills,' then he has the choice: If he wishes, he may go ahead, and if he wishes he may not."
Hadith Referenceسنن نسائي / كتاب الأيمان والنذور / 3861