Musnad Ahmad 27:1534

Yunus narrated to us, Fulayh narrated to us, from Sa'id ibn al-Harith, that he heard Abdullah ibn Umar [say] that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, a vow does not bring anything forward, nor does it delay it; rather, by the vow, [something] is extracted from the miser."