The Prophet ﷺ said (that Allah said), "Vowing does not bring to the son of Adam anything I have not already written in his fate, but vowing is imposed on him by way of fore ordainment. Through vowing I make a miser spend of his wealth."  

عَنِ النَّبِيِّ ﷺ قَالَ لاَ يَأْتِي ابْنَ آدَمَ النَّذْرُ بِشَىْءٍ لَمْ يَكُنْ قَدْ قَدَّرْتُهُ وَلَكِنْ يُلْقِيهِ الْقَدَرُ وَقَدْ قَدَّرْتُهُ لَهُ أَسْتَخْرِجُ بِهِ مِنَ الْبَخِيلِ  

The Prophet ﷺ said, "Allah says, 'The vow, does not bring about for the son of Adam anything I have not decreed for him, but his vow may coincide with what has been decided for him, and by this way I cause a miser to spend of his wealth. So he gives Me (spends in charity) for the fulfillment of what has been decreed for him what he would not give Me before but for his vow."  

قَالَ النَّبِيُّ ﷺ لاَ يَأْتِي ابْنَ آدَمَ النَّذْرُ بِشَىْءٍ لَمْ يَكُنْ قُدِّرَ لَهُ وَلَكِنْ يُلْقِيهِ النَّذْرُ إِلَى الْقَدَرِ قَدْ قُدِّرَ لَهُ فَيَسْتَخْرِجُ اللَّهُ بِهِ مِنَ الْبَخِيلِ فَيُؤْتِي عَلَيْهِ مَا لَمْ يَكُنْ يُؤْتِي عَلَيْهِ مِنْ قَبْلُ  

The Messenger of Allah ﷺ as saying: A vow does not provide for the son of Adam anything which I did not decree for him, but a vow draws it. A Divine decree is one which I have destined, it is extracted from a miser. He is given what he was not given before. (Using translation from Abū Dāʾūd 3288)   

وَقَالَ رَسُولُ اللهِ ﷺ لَا يَأْتِي ابْنَ آدَمَ النَّذْرُ بِشَيْءٍ لَمْ أَكُنْ قَدَّرْتُهُ لَهُ وَلَكِنَّهُ يَلْقِيهِ النَّذْرُ بِمَا قد قَدَّرْتُهُ لَهُ يُسْتَخْرَجُ بِهِ مِنَ الْبَخِيلِ يُؤْتِينِي عَلَيْهِ مَا لَمْ يَكُنْ آتَانِي عَلَيْهِ مِنْ قَبْلُ  

"قَال اللهُ -تَعَالى-: يأتِي ابنَ آدم النذَرُ بِشَيْءٍ لَم أكُن قدرتهُ، ولكِن يُلقِيه النذرُ إِلَى الْقَدرَ وَقَد قَدرتُهُ لَهُ أسْتَخْرِجُ به مِن البَخيل فيؤتينى عليه ما لم يكن يؤتينى (*) عليه من قبل".