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."
Sahih al-Bukhari Book 83, Hadith 71
← Previous Hadith The Prophet (ﷺ) forbade the making of vows and said, "It (a vow) does not prevent anything (that has to take place), but the property of a miser is spent (taken out) with it."

Sahih al-Bukhari Book 83, Hadith 70 Next Hadith → `Imran bin Hussain said, "The Prophet (ﷺ) said, 'The best of you (people) are my generation, and the second best will be those who will follow them, and then those who will follow the second generation." `Imran added, "I do not remember whether he mentioned two or three (generations) after his generation. He added, 'Then will come some people who will make vows but will not fulfill them; and they will be dishonest and will not be trustworthy, and they will give their witness without being asked to give their witness, and fatness will appear among them.' "

Sahih al-Bukhari Book 83, Hadith 72