حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ الزُّهْرِيُّ، حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنْ أَيُّوبَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، رِوَايَةً قَالَ " مَنْ حَلَفَ وَاسْتَثْنَى فَلَمْ يَحْنَثْ " .
It was narrated from Ibn 'Umar: "Whoever swears an oath and says In sha' Allah, will never break his oath." Translation Not Available
Book Ref: Sunan Ibn Majah Book 11 Hadith 2106
Web Ref: Sunan Ibn Majah Vol 3 Book 11 Hadith 2106