أَخْبَرَنَا مُحَمَّدُ بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ أَيُّوبَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ حَلَفَ فَقَالَ إِنْ شَاءَ اللَّهُ فَقَدِ اسْتَثْنَى " .
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.'" Translation Not Available
Book Ref: Sunan An Nisai Book 35 Hadith 3829
Web Ref: Sunan An Nisai Vol 4 Book 35 Hadith 3860