Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
ibnmajah:2117 – Hishām b. ʿAmmār > ʿĪsá b. Yūnus > al-Ajlaḥ al-Kindī > Yazīd b. al-Aṣam > Ibn ʿAbbās

'When anyone of you swears an oath, let him not say: 'What Allah wills and what you will.' Rather let him say: 'What Allah wills and then what you will.'  

ابن ماجة:٢١١٧ – حَدَّثَنَا هِشَامُ بْنُ عَمَّارٍ حَدَّثَنَا عِيسَى بْنُ يُونُسَ حَدَّثَنَا الأَجْلَحُ الْكِنْدِيُّ عَنْ يَزِيدَ بْنِ الأَصَمِّ عَنِ ابْنِ عَبَّاسٍ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا حَلَفَ أَحَدُكُمْ فَلاَ يَقُلْ مَا شَاءَ اللَّهُ وَشِئْتَ وَلَكِنْ لِيَقُلْ مَا شَاءَ اللَّهُ ثُمَّ شِئْتَ  

See similar narrations below:

Collected by Suyūṭī
suyuti:1684a –

'When anyone of you swears an oath, let him not say: 'What Allah wills and what you will.' Rather let him say: 'What Allah wills and then what you will.' (Using translation from Ibn Mājah 2117)   

السيوطي:١٦٨٤a –

"إِذا حَلفَ أحدُكُمْ فلا يَقُلْ: ما شاء اللهُ وشِئتُ ولكن ليقُلْ: ما شَاءَ اللهُ ثم شِئْتُه".  

[هـ] ابن ماجة عن ابن عباس