Narrator:Abdullāh ibn ‘Umar
أَخْبَرَنِي أَحْمَدُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا حِبَّانُ، قَالَ حَدَّثَنَا عَبْدُ الْوَارِثِ، قَالَ حَدَّثَنَا أَيُّوبُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ
" مَنْ حَلَفَ فَاسْتَثْنَى فَإِنْ شَاءَ مَضَى وَإِنْ شَاءَ تَرَكَ غَيْرَ حَنِثٍ "
It was narrated from Ibn 'Umar that the Prophet said:
"Whoever swears an oath and says: 'If Allah wills', then if he wishes he may go ahead, and if he wishes he may not, without having broken his oath."
Reported by An-Nasa’i (No. 3793), Abu Dawud (No. 3262), Ibn Majah (No. 2105) and Ahmad (No. 6126).