Sahih Muslim Book 26, Hadith 8
It does not avert Fate, but is the means by which something is extracted from the miser.
Do not take vows, for a vow has no effect against Fate; it is only from the miserly that something is extracted.
The vow does not bring anything near to the son of Adam which Allah has not ordained for him, but (at times) the vow coincides with Destiny, and this is how something is extracted from the miserly person, which that miser was not willing to give.