The Book of Vows (Kitab Al-Nadhr)
Muslim :: Book 14 : Hadith 4030
Abu Huraira reported: Allah's Apostle (may peace be upon him) found an old man walking between his two sons supported by them, whereupon Allah's Apostle (may peace be upon him) said: What is the matter with him? He (the narrator) said: Allah's Messenger, they are his sons and there is upon him the (fulfilment) of the vow, whereupon Allah's Apostle (may peace be upon him) said: Ride, old man, for Allah is not in need of you and your vow.