The prohibition of vows
حَدَّثَنَا أَحْمَدُ بْنُ يُوسُفَ، حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ سُفْيَانَ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " إِنَّ النَّذْرَ لاَ يَأْتِي ابْنَ آدَمَ بِشَىْءٍ إِلاَّ مَا قُدِّرَ لَهُ وَلَكِنْ يَغْلِبُهُ الْقَدَرُ مَا قُدِّرَ لَهُ فَيُسْتَخْرَجُ بِهِ مِنَ الْبَخِيلِ فَيَتَيَسَّرُ عَلَيْهِ مَا لَمْ يَكُنْ يَتَيَسَّرُ عَلَيْهِ مِنْ قَبْلِ ذَلِكَ وَقَدْ قَالَ اللَّهُ أَنْفِقْ أُنْفِقْ عَلَيْكَ " .
It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said: "Vows do not bring the son of Adam anything unless it has been decreed for him. But he is dominated by Divine preordainment, and will get what is decreed for him. And (vows) are a means of making the miser give something, so what he desires becomes obtainable for him, which was not obtainable before his vow. And Allah says: 'Spend, I will spend on you.'